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Xuan W, Ma JA. Pinpointing Acidic Residues in Proteins. ChemMedChem 2024; 19:e202300623. [PMID: 38303683 DOI: 10.1002/cmdc.202300623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 12/18/2023] [Indexed: 02/03/2024]
Abstract
It is of great importance to pinpoint specific residues or sites of a protein in biological contexts to enable desired mechanism of action for small molecules or to precisely control protein function. In this regard, acidic residues including aspartic acid (Asp) and glutamic acid (Glu) hold great potential due to their great prevalence and unique function. To unlock the largely untapped potential, great efforts have been made recently by synthetic chemists, chemical biologists and pharmacologists. Herein, we would like to highlight the remarkable progress and particularly introduce the electrophiles that exhibit reactivity to carboxylic acids, the light-induced reactivities to carboxylic acids and the genetically encoded noncanonical amino acids that allow protein manipulations at acidic residues. We also comment on certain unresolved challenges, hoping to draw more attention to this rapidly developing area.
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Affiliation(s)
- Weimin Xuan
- Frontiers Science Center for Synthetic Biology, Tianjin Key Laboratory of Function and Application of Biological Macromolecular Structures, School of Life Sciences, Tianjin University, Tianjin, 300072, China
| | - Jun-An Ma
- Department of Chemistry, Frontiers Science Center for Synthetic Biology, Tianjin University, Tianjin, 300072, P. R. China
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2
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Rahikainen R, Vester SK, Turkki P, Janosko CP, Deiters A, Hytönen VP, Howarth M. Visible light-induced specific protein reaction delineates early stages of cell adhesion. bioRxiv 2023:2023.07.21.549850. [PMID: 37503248 PMCID: PMC10370186 DOI: 10.1101/2023.07.21.549850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Light is well established for control of bond breakage, but not for control of specific bond formation in complex environments. We previously engineered diffusion-limited reactivity of SpyTag003 peptide with its protein partner SpyCatcher003 through spontaneous transamidation. This system enables precise and irreversible assembly of biological building blocks, with applications from biomaterials to vaccines. Here, we establish a system for rapid control of this amide bond formation with visible light. We have generated a caged SpyCatcher003, which allows light triggering of covalent bond formation to SpyTag003 in mammalian cells. Photocaging is achieved through site-specific incorporation of an unnatural coumarin-lysine at the reactive site of SpyCatcher003. We showed uniform specific reaction in cell lysate upon light activation. We then used the spatiotemporal precision of a 405 nm confocal laser for uncaging in seconds, probing the earliest events in mechanotransduction by talin, the key force sensor between the cytoskeleton and extracellular matrix. Reconstituting talin induced rapid biphasic extension of lamellipodia, revealing the kinetics of talin-regulated cell spreading and polarization. Thereafter we determined the hierarchy of recruitment of key components for cell adhesion. Precise control over site-specific protein reaction with visible light creates diverse opportunities for cell biology and nanoassembly.
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Affiliation(s)
- Rolle Rahikainen
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön katu 34, 33520, Tampere, Finland and Fimlab Laboratories, Biokatu 4, 33520, Tampere, Finland
| | - Susan K. Vester
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
- Current address: Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London, SE1 1UL, UK
| | - Paula Turkki
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön katu 34, 33520, Tampere, Finland and Fimlab Laboratories, Biokatu 4, 33520, Tampere, Finland
| | - Chasity P. Janosko
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Alexander Deiters
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Vesa P. Hytönen
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön katu 34, 33520, Tampere, Finland and Fimlab Laboratories, Biokatu 4, 33520, Tampere, Finland
| | - Mark Howarth
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
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3
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Niu W, Guo J. Co-translational Installation of Posttranslational Modifications by Non-canonical Amino Acid Mutagenesis. Chembiochem 2023; 24:e202300039. [PMID: 36853967 PMCID: PMC10202221 DOI: 10.1002/cbic.202300039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 02/26/2023] [Accepted: 02/28/2023] [Indexed: 03/02/2023]
Abstract
Protein posttranslational modifications (PTMs) play critical roles in regulating cellular activities. Here we provide a survey of genetic code expansion (GCE) methods that were applied in the co-translational installation and studies of PTMs through noncanonical amino acid (ncAA) mutagenesis. We begin by reviewing types of PTM that have been installed by GCE with a focus on modifications of tyrosine, serine, threonine, lysine, and arginine residues. We also discuss examples of applying these methods in biological studies. Finally, we end the piece with a short discussion on the challenges and the opportunities of the field.
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Affiliation(s)
- Wei Niu
- Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, N-68588, USA
- The Nebraska Center for Integrated Biomolecular Communication (NCIBC), University of Nebraska-Lincoln, Lincoln, NE-68588, USA
| | - Jiantao Guo
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE-68588, USA
- The Nebraska Center for Integrated Biomolecular Communication (NCIBC), University of Nebraska-Lincoln, Lincoln, NE-68588, USA
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4
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Batugal T, Pendyala G, Tomasovic L, Varner C, Caplin JD, Page AM, Davis M, Satola SW, García AJ, Kane RS. Engineering active lysostaphin variants that incorporate noncanonical amino acids and characterizing the effects of site-specific PEGylation. Biotechnol Bioeng 2023; 120:1694-1701. [PMID: 36810983 DOI: 10.1002/bit.28360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 02/11/2023] [Accepted: 02/19/2023] [Indexed: 02/24/2023]
Abstract
We describe a facile strategy to identify sites for the incorporation of noncanonical amino acids into lysostaphin-an enzyme that degrades the cell wall of Staphylococcus aureus-while retaining stapholytic activity. We used this strategy to generate active variants of lysostaphin incorporating para-azidophenylalanine. The incorporation of this "reactive handle" enabled the orthogonal site-specific modification of the enzyme variants with polyethylene glycol (PEG) using copper-free click cycloaddition. PEGylated lysostaphin variants could retain their stapholytic activity, with the extent of retention depending on the site of modification and the PEG molecular weight. The site-specific modification of lysostaphin could be useful not only for PEGylation to improve biocompatibility but also for the incorporation of the enzyme into hydrogels and other biomaterials and for studies of protein structure and dynamics. Moreover, the approach described herein could be readily applied to identify suitable sites for the incorporation of reactive handles into other proteins of interest.
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Affiliation(s)
- Troy Batugal
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Geetanjali Pendyala
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Luke Tomasovic
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Chad Varner
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Jeremy D Caplin
- Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA.,Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Alexander M Page
- Department of Medicine, Division of Infectious Diseases and Emory Investigational Clinical Microbiology Core, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Michelle Davis
- Department of Medicine, Division of Infectious Diseases and Emory Investigational Clinical Microbiology Core, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Sarah W Satola
- Department of Medicine, Division of Infectious Diseases and Emory Investigational Clinical Microbiology Core, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Andrés J García
- Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA.,Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Ravi S Kane
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA.,Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA
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5
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Xu C, Zou Q, Tian J, Li M, Xing B, Gong J, Wang J, Huo YX, Guo S. Simplified Construction of Engineered Bacillus subtilis Host for Improved Expression of Proteins Harboring Noncanonical Amino Acids. ACS Synth Biol 2023; 12:583-595. [PMID: 36653175 DOI: 10.1021/acssynbio.2c00604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The UAG-based genetic code expansion (GCE) enables site-specific incorporation of noncanonical amino acids (ncAAs) harboring novel chemical functionalities in specific target proteins. However, most GCE studies were done in several whole-genome engineered chassis cells whose hundreds of UAG stop codons were systematically edited to UAA to avoid readthrough in protein synthesis in the presence of GCE. The huge workload of removing all UAG limited the application of GCE in other microbial cell factories (MCF) such as Bacillus subtilis, which has 607 genes ended with UAG among its 4245 coding genes. Although the 257 essential genes count only 6.1% of the genes in B. subtilis, they transcribe 12.2% of the mRNAs and express 52.1% of the proteins under the exponential phase. Here, we engineered a strain named Bs-22 in which all 22 engineerable UAG stop codons in essential genes were edited to UAA via CRISPR/Cas9-mediated multiple-site engineering to minimize the negative effect of GCE on the expression of essential genes. Besides the process of constructing GCE-compatible B. subtilis was systematically optimized. Compared with wild-type B. subtilis (Bs-WT), the fluorescence signal of the eGFP expression could enhance 2.25-fold in Bs-22, and the production of protein tsPurple containing l-(7-hydroxycoumarin-4-yl) ethylglycine (Cou) was increased 2.31-fold in Bs-22. We verified that all purified tsPurple proteins from Bs-22 contained Cou, indicating the excellent fidelity of the strategy. This proof-of-concept study reported efficient overexpression of ncAA-rich proteins in MCF with minimized engineering, shedding new light on solving the trade-off between efficiency and workload.
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Affiliation(s)
- Changgeng Xu
- Key Laboratory of Molecular Medicine and Biotherapy, School of Life Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, 100081 Beijing, China
| | - Qin Zou
- Key Laboratory of Molecular Medicine and Biotherapy, School of Life Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, 100081 Beijing, China.,Beijing Institute of Technology (Tangshan) Translational Research Center, Tangshan Port Economic Development Zone, 063611 Hebei, China
| | - Jiheng Tian
- Key Laboratory of Molecular Medicine and Biotherapy, School of Life Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, 100081 Beijing, China
| | - Mengyuan Li
- Key Laboratory of Molecular Medicine and Biotherapy, School of Life Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, 100081 Beijing, China
| | - Baowen Xing
- Key Laboratory of Molecular Medicine and Biotherapy, School of Life Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, 100081 Beijing, China
| | - Julia Gong
- Marymount High School, Los Angeles, California 10643, United States
| | - Jiangyun Wang
- Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, 100101 Beijing, China
| | - Yi-Xin Huo
- Key Laboratory of Molecular Medicine and Biotherapy, School of Life Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, 100081 Beijing, China.,Beijing Institute of Technology (Tangshan) Translational Research Center, Tangshan Port Economic Development Zone, 063611 Hebei, China
| | - Shuyuan Guo
- Key Laboratory of Molecular Medicine and Biotherapy, School of Life Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, 100081 Beijing, China
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Mattheisen JM, Wollowitz JS, Huber T, Sakmar TP. Genetic code expansion to enable site-specific bioorthogonal labeling of functional G protein-coupled receptors in live cells. Protein Sci 2023; 32:e4550. [PMID: 36540928 PMCID: PMC9847076 DOI: 10.1002/pro.4550] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/13/2022] [Accepted: 12/17/2022] [Indexed: 12/24/2022]
Abstract
For use in site-specific bioorthogonal labeling of expressed G protein-coupled receptors (GPCRs) in live cells, we developed a luciferase-based reporter assay. The assay was used to compare amber codon suppression efficiency, receptor functionality, and efficiency of different bioorthogonal labeling chemistries. We used the assay system to compare side-by-side the efficiency of incorporation of three different noncanonical amino acids [4-azido-l-phenylalanine (azF), cyclopropene-l-lysine (CpK), and trans-cyclooct-2-en-l-lysine (TCOK)] at three different sites on a GPCR using three different genetic code expansion plasmid systems. As a model GPCR, we engineered an epitope-tagged C-C chemokine receptor 5 (CCR5)-RLuc3 fusion for expression in HEK293T cells. Satisfactory incorporation of azF, CpK, and TCOK into heterologously expressed CCR5 was achieved. We also carried out cell-based calcium mobilization assays to measure the function of the engineered CCR5, and in the same cells, we performed bioorthogonal labeling of the engineered mutants using heterobivalent compounds containing bioorthogonal tethering groups linked to either a small-molecule fluorophore or a peptide. Favorable reaction kinetics of tetrazine-containing compounds with CCR5 harboring TCOK was observed. However, bioorthogonal labeling in live cells of CCR5 harboring CpK with tetrazine-containing compounds using the inverse electron demand Diels-Alder ligation was overall slightly more efficient than other reactions tested.
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Affiliation(s)
- Jordan M. Mattheisen
- Laboratory of Chemical Biology and Signal TransductionThe Rockefeller UniversityNew YorkNew YorkUSA
- Tri‐Institutional PhD Program in Chemical BiologyNew YorkNew YorkUSA
| | - Jaina S. Wollowitz
- Laboratory of Chemical Biology and Signal TransductionThe Rockefeller UniversityNew YorkNew YorkUSA
- Tri‐Institutional PhD Program in Chemical BiologyNew YorkNew YorkUSA
| | - Thomas Huber
- Laboratory of Chemical Biology and Signal TransductionThe Rockefeller UniversityNew YorkNew YorkUSA
| | - Thomas P. Sakmar
- Laboratory of Chemical Biology and Signal TransductionThe Rockefeller UniversityNew YorkNew YorkUSA
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7
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Lummis SCR, Dougherty DA. Expression of Mutant Glycine Receptors in Xenopus Oocytes Using Canonical and Non-Canonical Amino Acids Reveals Distinct Roles of Conserved Proline Residues. Membranes (Basel) 2022; 12:1012. [PMID: 36295771 PMCID: PMC9607081 DOI: 10.3390/membranes12101012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/05/2022] [Accepted: 10/08/2022] [Indexed: 06/16/2023]
Abstract
Pentameric ligand-gated ion channels (pLGIC) play important roles in fast neuronal signal transmission. Functional receptors are pentamers, with each subunit having an extracellular domain (ECD), a transmembrane domain (TMD) and an intracellular domain. The binding of the agonist to the ECD induces a structural change that is transduced to the TMD to open the channel. Molecular details of this process are emerging, but a comprehensive understanding is still lacking. Proline (Pro) is one amino acid that has attracted much interest; its unusual features generate bends in loops and kinks and bulges in helices, which can be essential for function in some pLGICs. Here, we explore the roles of four conserved Pros in the glycine receptor (GlyR), creating substitutions with canonical and noncanonical amino acids, characterizing them using two electrode voltage clamp electrophysiology in Xenopus oocytes, and interpreting changes in receptor parameters using structural data from the open and closed states of the receptor. The data reveal that for efficient function, the Pro in the α1β1 loop is needed to create a turn and to be the correct size and shape to interact with nearby residues; the peptide bond of the Pro in the Cys-loop requires the cis conformation; and the Pros in loop A and M1 allow efficient function because of their reduced hydrogen bonding capacity. These data are broadly consistent with data from other pLGICs, and therefore likely represent the important features of these Pros in all members of the family.
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Affiliation(s)
- Sarah C. R. Lummis
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK
| | - Dennis A. Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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Wu K, Moore JA, Miller MD, Chen Y, Lee C, Xu W, Peng Z, Duan Q, Phillips GN, Uribe RA, Xiao H. Expanding the eukaryotic genetic code with a biosynthesized 21st amino acid. Protein Sci 2022; 31:e4443. [PMID: 36173166 PMCID: PMC9601876 DOI: 10.1002/pro.4443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Revised: 08/18/2022] [Accepted: 08/24/2022] [Indexed: 01/31/2023]
Abstract
Genetic code expansion technology allows for the use of noncanonical amino acids (ncAAs) to create semisynthetic organisms for both biochemical and biomedical applications. However, exogenous feeding of chemically synthesized ncAAs at high concentrations is required to compensate for the inefficient cellular uptake and incorporation of these components into proteins, especially in the case of eukaryotic cells and multicellular organisms. To generate organisms capable of autonomously biosynthesizing an ncAA and incorporating it into proteins, we have engineered a metabolic pathway for the synthesis of O-methyltyrosine (OMeY). Specifically, we endowed organisms with a marformycins biosynthetic pathway-derived methyltransferase that efficiently converts tyrosine to OMeY in the presence of the co-factor S-adenosylmethionine. The resulting cells can produce and site-specifically incorporate OMeY into proteins at much higher levels than cells exogenously fed OMeY. To understand the structural basis for the substrate selectivity of the transferase, we solved the X-ray crystal structures of the ligand-free and tyrosine-bound enzymes. Most importantly, we have extended this OMeY biosynthetic system to both mammalian cells and the zebrafish model to enhance the utility of genetic code expansion. The creation of autonomous eukaryotes using a 21st amino acid will make genetic code expansion technology more applicable to multicellular organisms, providing valuable vertebrate models for biological and biomedical research.
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Affiliation(s)
- Kuan‐Lin Wu
- Department of ChemistryRice UniversityHoustonTexasUSA
| | - Joshua A. Moore
- Department of BiosciencesRice UniversityHoustonTexasUSA
- Biochemistry and Cell Biology ProgramRice UniversityHoustonTexasUSA
| | | | - Yuda Chen
- Department of ChemistryRice UniversityHoustonTexasUSA
| | - Catherine Lee
- Department of ChemistryRice UniversityHoustonTexasUSA
| | - Weijun Xu
- Department of BiosciencesRice UniversityHoustonTexasUSA
| | - Zane Peng
- Department of ChemistryRice UniversityHoustonTexasUSA
| | - Qinghui Duan
- Department of ChemistryRice UniversityHoustonTexasUSA
| | - George N. Phillips
- Department of ChemistryRice UniversityHoustonTexasUSA
- Department of BiosciencesRice UniversityHoustonTexasUSA
| | - Rosa A. Uribe
- Department of BiosciencesRice UniversityHoustonTexasUSA
- Biochemistry and Cell Biology ProgramRice UniversityHoustonTexasUSA
| | - Han Xiao
- Department of ChemistryRice UniversityHoustonTexasUSA
- Department of BiosciencesRice UniversityHoustonTexasUSA
- Department of BioengineeringRice UniversityHoustonTexasUSA
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McManus D, Polidarova L, Smyllie NJ, Patton AP, Chesham JE, Maywood ES, Chin JW, Hastings MH. Cryptochrome 1 as a state variable of the circadian clockwork of the suprachiasmatic nucleus: Evidence from translational switching. Proc Natl Acad Sci U S A 2022; 119:e2203563119. [PMID: 35976881 PMCID: PMC9407638 DOI: 10.1073/pnas.2203563119] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The suprachiasmatic nucleus (SCN) of the hypothalamus is the principal clock driving circadian rhythms of physiology and behavior that adapt mammals to environmental cycles. Disruption of SCN-dependent rhythms compromises health, and so understanding SCN time keeping will inform management of diseases associated with modern lifestyles. SCN time keeping is a self-sustaining transcriptional/translational delayed feedback loop (TTFL), whereby negative regulators inhibit their own transcription. Formally, the SCN clock is viewed as a limit-cycle oscillator, the simplest being a trajectory of successive phases that progresses through two-dimensional space defined by two state variables mapped along their respective axes. The TTFL motif is readily compatible with limit-cycle models, and in Neurospora and Drosophila the negative regulators Frequency (FRQ) and Period (Per) have been identified as state variables of their respective TTFLs. The identity of state variables of the SCN oscillator is, however, less clear. Experimental identification of state variables requires reversible and temporally specific control over their abundance. Translational switching (ts) provides this, the expression of a protein of interest relying on the provision of a noncanonical amino acid. We show that the negative regulator Cryptochrome 1 (CRY1) fulfills criteria defining a state variable: ts-CRY1 dose-dependently and reversibly suppresses the baseline, amplitude, and period of SCN rhythms, and its acute withdrawal releases the TTFL to oscillate from a defined phase. Its effect also depends on its temporal pattern of expression, although constitutive ts-CRY1 sustained (albeit less stable) oscillations. We conclude that CRY1 has properties of a state variable, but may operate among several state variables within a multidimensional limit cycle.
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Affiliation(s)
- David McManus
- aNeurobiology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Lenka Polidarova
- aNeurobiology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Nicola J. Smyllie
- aNeurobiology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Andrew P. Patton
- aNeurobiology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Johanna E. Chesham
- aNeurobiology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Elizabeth S. Maywood
- aNeurobiology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Jason W. Chin
- bPNAC Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, CB2 0QH, United Kingdom
| | - Michael H. Hastings
- aNeurobiology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
- 1To whom correspondence may be addressed.
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Abstract
![]()
5-HT3 receptors are members of the family
of pentameric
ligand-gated ion channels. Each subunit has an extracellular, transmembrane,
and intracellular domain. Only part of the intracellular domain structure
has been solved, revealing it contains two α-helical segments;
one, the MA helix, is an extension of M4, while the other, the MX
helix, is formed from residues located close to the end of M3. This
MX helix is in distinct locations in open and closed receptor structures,
suggesting it may play a role in function. Here, we explore this hypothesis
using functional responses of Ala-substituted mutant receptors expressed
in HEK293 cells. The data show altering many of the MX residues results
in a small decrease in EC50 (up to 5-fold), although in
one (H232A) this is increased. Radiolabeled ligand binding on selected
mutants showed no change in binding affinity, indicating an effect
on gating and not binding. In addition, five mutations (P316A, V317A,
P318A, D319A, and H323A) initially resulted in nonfunctional receptors,
but the function could be rescued by coexpression with a chaperone
protein, suggesting a likely role in assembly or folding. Examination
of previously obtained MD simulation data shows that the extent of
MX encompassed by membrane lipids differs considerably in the open
and closed structures, suggesting that lipid–protein interactions
in this region could have a major effect on channel opening propensity.
We conclude that the MX helix can modulate the function of the receptor
and propose that its interactions with membrane lipids play a major
role in this.
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Affiliation(s)
- James Mocatta
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Susanne M Mesoy
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Sarah C R Lummis
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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11
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Dean Cho CC, Blankenship LR, Ma X, Xu S, Liu W. The Pyrrolysyl-tRNA Synthetase Activity can be Improved by a P188 Mutation that Stabilizes the Full-Length Enzyme. J Mol Biol 2022; 434:167453. [PMID: 35033561 PMCID: PMC9018550 DOI: 10.1016/j.jmb.2022.167453] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Revised: 12/18/2021] [Accepted: 01/09/2022] [Indexed: 11/24/2022]
Abstract
The amber suppression-based noncanonical amino acid (ncAA) mutagenesis technique has been widely used in both basic and applied research. So far more than two hundred ncAAs have been genetically encoded by amber codon in both prokaryotes and eukaryotes using wild-type and engineered pyrrolysyl-tRNA synthetase (PylRS)-tRNAPyl (PylT) pairs. Methanosarcina mazei PylRS (MmPylRS) is arguably one of two most used PylRS variants. However, it contains an unstable N-terminal domain that is usually cleaved from the full-length protein during expression and therefore leads to a low enzyme activity. We discovered that the cleavage takes place after A189 and this cleavage is inhibited when MmPylRS is co-expressed with Ca. Methanomethylophilus alvus tRNAPyl (CmaPylT). In the presence of CmaPylT, MmPylRS is cleaved after an alternative site K110. MmPylRS is active toward CmaPylT. Its combined use with CmaPylT leads to enhanced incorporation of Nε-Boc-lysine (BocK) at amber codon. To prevent MmPylRS from cleavage after A189 in the presence of its cognate M. mazei tRNAPyl (MmPylT), we introduced mutations at P188. Our results indicated that the P188G mutation stabilizes MmPylRS. We showed that the P188G mutation in wild-type MmPylRS or its engineered variants allows enhanced incorporation of BocK and other noncanonical amino acids including Nε-acetyl-lysine when they are co-expressed with MmPylT.
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Affiliation(s)
- Chia-Chuan Dean Cho
- The Texas A&M Drug Discovery Laboratory, Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
| | - Lauren R Blankenship
- The Texas A&M Drug Discovery Laboratory, Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
| | - Xinyu Ma
- The Texas A&M Drug Discovery Laboratory, Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
| | - Shiqing Xu
- The Texas A&M Drug Discovery Laboratory, Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
| | - Wenshe Liu
- The Texas A&M Drug Discovery Laboratory, Department of Chemistry, Texas A&M University, College Station, TX 77843, USA; Institute of Biosciences and Technology and Department of Translational Medical Sciences, College of Medicine, Texas A&M University, Houston, TX 77030, USA; Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA; Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M University, College Station, TX 77843, USA.
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12
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Weaver JB, Lin CY, Faries KM, Mathews II, Russi S, Holten D, Kirmaier C, Boxer SG. Photosynthetic reaction center variants made via genetic code expansion show Tyr at M210 tunes the initial electron transfer mechanism. Proc Natl Acad Sci U S A 2021; 118:e2116439118. [PMID: 34907018 DOI: 10.1073/pnas.2116439118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2021] [Indexed: 11/18/2022] Open
Abstract
Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides were engineered to vary the electronic properties of a key tyrosine (M210) close to an essential electron transfer component via its replacement with site-specific, genetically encoded noncanonical amino acid tyrosine analogs. High fidelity of noncanonical amino acid incorporation was verified with mass spectrometry and X-ray crystallography and demonstrated that RC variants exhibit no significant structural alterations relative to wild type (WT). Ultrafast transient absorption spectroscopy indicates the excited primary electron donor, P*, decays via a ∼4-ps and a ∼20-ps population to produce the charge-separated state P+HA - in all variants. Global analysis indicates that in the ∼4-ps population, P+HA - forms through a two-step process, P*→ P+BA -→ P+HA -, while in the ∼20-ps population, it forms via a one-step P* → P+HA - superexchange mechanism. The percentage of the P* population that decays via the superexchange route varies from ∼25 to ∼45% among variants, while in WT, this percentage is ∼15%. Increases in the P* population that decays via superexchange correlate with increases in the free energy of the P+BA - intermediate caused by a given M210 tyrosine analog. This was experimentally estimated through resonance Stark spectroscopy, redox titrations, and near-infrared absorption measurements. As the most energetically perturbative variant, 3-nitrotyrosine at M210 creates an ∼110-meV increase in the free energy of P+BA - along with a dramatic diminution of the 1,030-nm transient absorption band indicative of P+BA - formation. Collectively, this work indicates the tyrosine at M210 tunes the mechanism of primary electron transfer in the RC.
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13
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Taylor NC, Nikić-Spiegel I. Film-like organelles equip cells with multiple genetic codes. Trends Biochem Sci 2021; 47:369-371. [PMID: 34895957 DOI: 10.1016/j.tibs.2021.11.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 11/19/2021] [Accepted: 11/19/2021] [Indexed: 10/19/2022]
Abstract
The simultaneous incorporation of distinct noncanonical amino acids into different proteins within eukaryotic cells remains challenging. This new study by Reinkemeier and Lemke demonstrates how 2D phase separation can be used to engineer spatially separated organelles. These film-like organelles translate proteins independently from each other and the canonical genetic code.
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Affiliation(s)
- Neil C Taylor
- Centre for Integrative Neuroscience, University of Tübingen, Otfried-Müller-Straße 25, 72076 Tübingen, Germany
| | - Ivana Nikić-Spiegel
- Centre for Integrative Neuroscience, University of Tübingen, Otfried-Müller-Straße 25, 72076 Tübingen, Germany. @cin.uni-tuebingen.de
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14
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Meineke B, Heimgärtner J, Craig AJ, Landreh M, Moodie LWK, Elsässer SJ. A Genetically Encoded Picolyl Azide for Improved Live Cell Copper Click Labeling. Front Chem 2021; 9:768535. [PMID: 34858945 PMCID: PMC8632528 DOI: 10.3389/fchem.2021.768535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 10/13/2021] [Indexed: 11/13/2022] Open
Abstract
Bioorthogonal chemistry allows rapid and highly selective reactivity in biological environments. The copper-catalyzed azide–alkyne cycloaddition (CuAAC) is a classic bioorthogonal reaction routinely used to modify azides or alkynes that have been introduced into biomolecules. Amber suppression is an efficient method for incorporating such chemical handles into proteins on the ribosome, in which noncanonical amino acids (ncAAs) are site specifically introduced into the polypeptide in response to an amber (UAG) stop codon. A variety of ncAA structures containing azides or alkynes have been proven useful for performing CuAAC chemistry on proteins. To improve CuAAC efficiency, biologically incorporated alkyne groups can be reacted with azide substrates that contain copper-chelating groups. However, the direct incorporation of copper-chelating azides into proteins has not been explored. To remedy this, we prepared the ncAA paz-lysine (PazK), which contains a picolyl azide motif. We show that PazK is efficiently incorporated into proteins by amber suppression in mammalian cells. Furthermore, PazK-labeled proteins show improved reactivity with alkyne reagents in CuAAC.
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Affiliation(s)
- Birthe Meineke
- Science for Life Laboratory, Department of Medical Biochemistry and Biophysics, Division of Genome Biology, Karolinska Institutet, Stockholm, Sweden.,Ming Wai Lau Centre for Reparative Medicine, Stockholm Node, Karolinska Institutet, Stockholm, Sweden
| | - Johannes Heimgärtner
- Science for Life Laboratory, Department of Medical Biochemistry and Biophysics, Division of Genome Biology, Karolinska Institutet, Stockholm, Sweden.,Ming Wai Lau Centre for Reparative Medicine, Stockholm Node, Karolinska Institutet, Stockholm, Sweden
| | - Alexander J Craig
- Drug Design and Discovery, Department of Medicinal Chemistry, Biomedical Centre, Uppsala University, Uppsala, Sweden
| | - Michael Landreh
- Department of Microbiology, Tumor and Cell Biology, Science for Life Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Lindon W K Moodie
- Drug Design and Discovery, Department of Medicinal Chemistry, Biomedical Centre, Uppsala University, Uppsala, Sweden.,Uppsala Antibiotic Centre, Uppsala University, Uppsala, Sweden
| | - Simon J Elsässer
- Science for Life Laboratory, Department of Medical Biochemistry and Biophysics, Division of Genome Biology, Karolinska Institutet, Stockholm, Sweden.,Ming Wai Lau Centre for Reparative Medicine, Stockholm Node, Karolinska Institutet, Stockholm, Sweden
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15
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Pan X, Yang J, Xie P, Zhang J, Ke F, Guo X, Liang M, Liu L, Wang Q, Gao X. Enhancement of Activity and Thermostability of Keratinase From Pseudomonas aeruginosa CCTCC AB2013184 by Directed Evolution With Noncanonical Amino Acids. Front Bioeng Biotechnol 2021; 9:770907. [PMID: 34733836 PMCID: PMC8558439 DOI: 10.3389/fbioe.2021.770907] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Accepted: 10/05/2021] [Indexed: 11/13/2022] Open
Abstract
A keratinase from Pseudomonas aeruginosa (KerPA), which belongs to the M4 family of metallopeptidases, was characterised in this study. This enzyme was engineered with non-canonical amino acids (ncAAs) using genetic code expansion. Several variants with enhanced activity and thermostability were identified and the most prominent, Y21pBpF/Y70pBpF/Y114pBpF, showed an increase in enzyme activity and half-life of approximately 1.3-fold and 8.2-fold, respectively. Considering that keratinases usually require reducing agents to efficiently degrade keratin, the Y21pBpF/Y70pBpF/Y114pBpF variant with enhanced activity and stability under reducing conditions may have great significance for practical applications. Molecular Dynamics (MD) was performed to identify the potential mechanisms underlying these improvements. The results showed that mutation with pBpF at specific sites of the enzyme could fill voids, form new interactions, and reshape the local structure of the active site of the enzyme.
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Affiliation(s)
- Xianchao Pan
- School of Pharmacy, Southwest Medical University, Luzhou, China
| | - Jian Yang
- School of Pharmacy, Southwest Medical University, Luzhou, China
| | - Peijuan Xie
- School of Pharmacy, Southwest Medical University, Luzhou, China
| | - Jing Zhang
- School of Pharmacy, Southwest Medical University, Luzhou, China
| | - Famin Ke
- School of Pharmacy, Southwest Medical University, Luzhou, China
| | - Xiurong Guo
- School of Pharmacy, Southwest Medical University, Luzhou, China
| | - Manyu Liang
- School of Pharmacy, Southwest Medical University, Luzhou, China
| | - Li Liu
- School of Pharmacy, Southwest Medical University, Luzhou, China
| | - Qin Wang
- School of Pharmacy, Southwest Medical University, Luzhou, China
| | - Xiaowei Gao
- School of Pharmacy, Southwest Medical University, Luzhou, China.,Department of Pharmacy, The Affiliated Hospital of Southwest Medical University, Luzhou, China.,Department of Chemistry, Zhejiang University, Hangzhou, China
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16
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Zagotta WN, Sim BS, Nhim AK, Raza MM, Evans EG, Venkatesh Y, Jones CM, Mehl RA, Petersson EJ, Gordon SE. An improved fluorescent noncanonical amino acid for measuring conformational distributions using time-resolved transition metal ion FRET. eLife 2021; 10:e70236. [PMID: 34623258 PMCID: PMC8500717 DOI: 10.7554/elife.70236] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 08/09/2021] [Indexed: 11/30/2022] Open
Abstract
With the recent explosion in high-resolution protein structures, one of the next frontiers in biology is elucidating the mechanisms by which conformational rearrangements in proteins are regulated to meet the needs of cells under changing conditions. Rigorously measuring protein energetics and dynamics requires the development of new methods that can resolve structural heterogeneity and conformational distributions. We have previously developed steady-state transition metal ion fluorescence resonance energy transfer (tmFRET) approaches using a fluorescent noncanonical amino acid donor (Anap) and transition metal ion acceptor to probe conformational rearrangements in soluble and membrane proteins. Here, we show that the fluorescent noncanonical amino acid Acd has superior photophysical properties that extend its utility as a donor for tmFRET. Using maltose-binding protein (MBP) expressed in mammalian cells as a model system, we show that Acd is comparable to Anap in steady-state tmFRET experiments and that its long, single-exponential lifetime is better suited for probing conformational distributions using time-resolved FRET. These experiments reveal differences in heterogeneity in the apo and holo conformational states of MBP and produce accurate quantification of the distributions among apo and holo conformational states at subsaturating maltose concentrations. Our new approach using Acd for time-resolved tmFRET sets the stage for measuring the energetics of conformational rearrangements in soluble and membrane proteins in near-native conditions.
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Affiliation(s)
- William N Zagotta
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Brandon S Sim
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Anthony K Nhim
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Marium M Raza
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Eric Gb Evans
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Yarra Venkatesh
- Department of Chemistry, University of Pennsylvania, Philadelphia, United States
| | - Chloe M Jones
- Department of Chemistry, University of Pennsylvania, Philadelphia, United States
- Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania, Philadelphia, United States
| | - Ryan A Mehl
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, United States
| | - E James Petersson
- Department of Chemistry, University of Pennsylvania, Philadelphia, United States
| | - Sharona E Gordon
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
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17
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Chen H, Wilson J, Ottinger S, Gan Q, Fan C. Introducing noncanonical amino acids for studying and engineering bacterial microcompartments. Curr Opin Microbiol 2021; 61:67-72. [PMID: 33813159 PMCID: PMC8169543 DOI: 10.1016/j.mib.2021.03.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Revised: 02/28/2021] [Accepted: 03/11/2021] [Indexed: 10/21/2022]
Abstract
Bacterial microcompartments (BMCs) with selectively permeable shells and encapsulated enzyme cores are well-suited candidates for nano-bioreactors because of their advantages of enhancing pathway flux and protection against toxic products. To better study and engineer protein-based BMCs, a series of protein chemistry approaches are adopted. As one of the most advanced techniques, genetic code expansion can introduce various noncanonical amino acids (ncAAs) with diverse functional groups into target proteins, thus providing powerful tools for protein studies and engineering. This review summarizes and proposes useful tools based on current development of the genetic code expansion technique towards challenges in BMC studies and engineering.
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Affiliation(s)
- Hao Chen
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, USA
| | - Jessica Wilson
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, USA
| | - Sara Ottinger
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR, USA
| | - Qinglei Gan
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR, USA
| | - Chenguang Fan
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, USA; Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR, USA.
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18
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Fang C, Drobizhev M, Ng HL, Pantazis P. Editorial: Mechanisms of Fluorescent Proteins. Front Mol Biosci 2021; 8:701523. [PMID: 34124168 PMCID: PMC8187757 DOI: 10.3389/fmolb.2021.701523] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 05/10/2021] [Indexed: 11/23/2022] Open
Affiliation(s)
- Chong Fang
- Department of Chemistry, Oregon State University, Corvallis, OR, United States
| | - Mikhail Drobizhev
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT, United States
| | - Ho Leung Ng
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, United States
| | - Periklis Pantazis
- Department of Bioengineering, Imperial College London, London, United Kingdom
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19
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Abstract
Antibodies possess properties that make them valuable as therapeutics, diagnostics, and basic research tools. However, antibody chemical reactivity and covalent antigen binding are constrained, or even prevented, by the narrow range of chemistries encoded in canonical amino acids. In this work, we investigate strategies for leveraging an expanded range of chemical functionality using yeast displayed antibodies containing noncanonical amino acids (ncAAs) in or near antibody complementarity determining regions (CDRs). To enable systematic characterization of the effects of ncAA incorporation on antibody function, we first investigated whether diversification of a single antibody loop would support the isolation of binding clones against immunoglobulins from three species. We constructed and screened a billion-member library containing canonical amino acid diversity and loop length diversity only within the third complementarity determining region of the heavy chain (CDR-H3). Isolated clones exhibited moderate affinities (double- to triple-digit nanomolar affinities) and, in several cases, single-species specificity, confirming that antibody specificity can be mediated by a single CDR. This constrained diversity enabled the utilization of additional CDRs for the installation of chemically reactive and photo-cross-linkable ncAAs. Binding studies of ncAA-substituted antibodies revealed that ncAA incorporation is reasonably well tolerated, with observed changes in affinity occurring as a function of ncAA side chain identity, substitution site, and the ncAA incorporation machinery used. Multiple azide-containing ncAAs supported copper-catalyzed azide-alkyne cycloaddition (CuAAC) and strain-promoted azide-alkyne cycloaddition (SPAAC) without the abrogation of binding function. Similarly, several alkyne substitutions facilitated CuAAC without the apparent disruption of binding. Finally, antibodies substituted with a photo-cross-linkable ncAA were evaluated for ultraviolet-mediated cross-linking on the yeast surface. Competition-based assays revealed position-dependent covalent linkages, strongly suggesting successful cross-linking. Key findings regarding CuAAC reactions and photo-cross-linking on the yeast surface were confirmed using soluble forms of ncAA-substituted clones. The consistency of findings on the yeast surface and in solution suggest that chemical diversification can be incorporated into yeast display screening approaches. Taken together, our results highlight the power of integrating the use of yeast display and ncAAs in search of proteins with "chemically augmented" binding functions. This includes strategies for systematically introducing small molecule functionality within binding protein structures and evaluating protein-based covalent target binding. The efficient preparation and chemical diversification of antibodies on the yeast surface open up new possibilities for discovering "drug-like" protein leads in high throughput.
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Affiliation(s)
- Mariha Islam
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States
| | - Haixing P. Kehoe
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States
| | - Jacob B. Lissoos
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States
| | - Manjie Huang
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States
| | - Christopher E. Ghadban
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States
| | - Greg B. Sánchez
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States
| | - Hanan Z. Lane
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States
| | - James A. Van Deventer
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States
- Biomedical Engineering Department, Tufts University, Medford, Massachusetts 02155, United States
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20
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Galindo Casas M, Stargardt P, Mairhofer J, Wiltschi B. Decoupling Protein Production from Cell Growth Enhances the Site-Specific Incorporation of Noncanonical Amino Acids in E. coli. ACS Synth Biol 2020; 9:3052-3066. [PMID: 33150786 DOI: 10.1021/acssynbio.0c00298] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The site-specific incorporation of noncanonical amino acids (ncAAs) into proteins by amber stop codon suppression has become a routine method in academic laboratories. This approach requires an amber suppressor tRNACUA to read the amber codon and an aminoacyl-tRNA synthetase to charge the tRNACUA with the ncAA. However, a major drawback is the low yield of the mutant protein in comparison to the wild type. This effect primarily results from the competition of release factor 1 with the charged suppressor tRNACUA for the amber codon at the A-site of the ribosome. A number of laboratories have attempted to improve the incorporation efficiency of ncAAs with moderate results. We aimed at increasing the efficiency to produce high yields of ncAA-functionalized proteins in a scalable setting for industrial application. To do this, we inserted an ncAA into the enhanced green fluorescent protein and an antibody mimetic molecule using an industrial E. coli strain, which produces recombinant proteins independent of cell growth. The controlled decoupling of recombinant protein production from cell growth considerably increased the incorporation of the ncAA, producing substantially higher protein yields versus the reference E. coli strain BL21(DE3). The target proteins were expressed at high levels, and the ncAA was efficiently incorporated with excellent fidelity while the protein function was preserved.
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Affiliation(s)
- Meritxell Galindo Casas
- acib − Austrian Center of Industrial Biotechnology, 8010 Graz, Austria
- Institute of Molecular Biotechnology, Graz University of Technology, 8010 Graz, Austria
| | | | | | - Birgit Wiltschi
- acib − Austrian Center of Industrial Biotechnology, 8010 Graz, Austria
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21
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Yong KW, Yuen D, Chen MZ, Johnston APR. Engineering the Orientation, Density, and Flexibility of Single-Domain Antibodies on Nanoparticles To Improve Cell Targeting. ACS Appl Mater Interfaces 2020; 12:5593-5600. [PMID: 31917547 DOI: 10.1021/acsami.9b20993] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Nanoparticles targeted to specific cells have the potential to improve the delivery of therapeutics. The effectiveness of cell targeting can be significantly improved by optimizing how the targeting ligands are displayed on the nanoparticle surface. Crucial to optimizing the cell binding are the orientation, density, and flexibility of the targeting ligand on the nanoparticle surface. In this paper, we used an anti-EGFR single-domain antibody (sdAb or nanobody) to target fluorescent nanocrystals (Qdots) to epidermal growth factor receptor (EGFR)-positive cells. The sdAbs were expressed with a synthetic amino acid (azPhe), enabling site-specific conjugation to Qdots in an improved orientation. To optimize the targeting efficiency, we engineered the point of attachment (orientation), controlled the density of targeting groups on the surface of the Qdot, and optimized the length of the poly(ethylene glycol) linker used to couple the sdAb to the Qdot surface. By optimizing orientation, density, and flexibility, we improved cell targeting by more than an order of magnitude. This work highlights the importance of understanding the structure of the nanoparticle surface to achieve the optimal interactions with the intended receptors and how engineering the nanoparticle surface can significantly improve cell targeting.
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Affiliation(s)
- Ken W Yong
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , Victoria 3052 , Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology , Monash University , Parkville , Victoria 3052 , Australia
| | - Daniel Yuen
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , Victoria 3052 , Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology , Monash University , Parkville , Victoria 3052 , Australia
| | - Moore Z Chen
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , Victoria 3052 , Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology , Monash University , Parkville , Victoria 3052 , Australia
| | - Angus P R Johnston
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , Victoria 3052 , Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology , Monash University , Parkville , Victoria 3052 , Australia
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22
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Abstract
We previously engineered the β-subunit of tryptophan synthase (TrpB), which catalyzes the condensation of l-serine and indole to l-tryptophan, to synthesize a range of noncanonical amino acids from l-serine and indole derivatives or other nucleophiles. Here we employ directed evolution to engineer TrpB to accept 3-substituted oxindoles and form C-C bonds leading to new quaternary stereocenters. Initially, the variants that could use 3-substituted oxindoles preferentially formed N-C bonds on N1 of the substrate. Protecting N1 encouraged evolution toward C-alkylation, which persisted when protection was removed. Six generations of directed evolution resulted in TrpB Pfquat with a 400-fold improvement in activity for alkylation of 3-substituted oxindoles and the ability to selectively form a new, all-carbon quaternary stereocenter at the γ-position of the amino acid products. The enzyme can also alkylate and form all-carbon quaternary stereocenters on structurally similar lactones and ketones, where it exhibits excellent regioselectivity for the tertiary carbon. The configurations of the γ-stereocenters of two of the products were determined via microcrystal electron diffraction (MicroED), and we report the MicroED structure of a small molecule obtained using the Falcon III direct electron detector. Highly thermostable and expressed at >500 mg/L E. coli culture, TrpB Pfquat offers an efficient, sustainable, and selective platform for the construction of diverse noncanonical amino acids bearing all-carbon quaternary stereocenters.
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Affiliation(s)
- Markus Dick
- Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Nicholas S. Sarai
- Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Michael W. Martynowycz
- Howard Hughes Medical Institute, David Geffen School of Medicine, Departments of Biological Chemistry and Physiology, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Tamir Gonen
- Howard Hughes Medical Institute, David Geffen School of Medicine, Departments of Biological Chemistry and Physiology, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Frances H. Arnold
- Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
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23
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Abstract
C-C bond-forming reactions often require nucleophilic carbon species rarely compatible with aqueous reaction media, thus restricting their appearance in biocatalysis. Here we report the use of nitroalkanes as a structurally versatile class of nucleophilic substrates for C-C bond formation catalyzed by variants of the β-subunit of tryptophan synthase (TrpB). The enzymes accept a wide range of nitroalkanes to form noncanonical amino acids, here the nitro group can serve as a handle for further modification. Using nitroalkane nucleophiles greatly expands the scope of compounds made by TrpB variants and establishes nitroalkanes as a valuable substrate class for biocatalytic C-C bond formation.
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Affiliation(s)
- David K. Romney
- Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Nicholas S. Sarai
- Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Frances H. Arnold
- Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
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24
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Mosesso R, Dougherty DA, Lummis SCR. Proline Residues in the Transmembrane/Extracellular Domain Interface Loops Have Different Behaviors in 5-HT 3 and nACh Receptors. ACS Chem Neurosci 2019; 10:3327-3333. [PMID: 31273982 DOI: 10.1021/acschemneuro.9b00315] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Cys-loop receptors are important drug targets that are involved in signaling in the nervous system. The binding of neurotransmitters in the extracellular region of these receptors triggers an allosteric activation mechanism, the full details of which remain elusive, although structurally flexible loops in the interface between the extracellular region of Cys-loop receptors and the pore-forming transmembrane domain are known to play an important role. Here we explore the roles of three largely conserved Pro residues in two of these loops, the Cys-loop and M2-M3 loop, in 5-HT3A and α7 nACh receptors. The data from natural and noncanonical amino acid mutagenesis suggest that in both proteins a Pro is essential in the Cys-loop, probably because of its enhanced ability to form a cis peptide bond, although other factors are also involved. The important characteristics of Pros in the M2-M3 loop, however, differ in these two receptors: in the 5-HT3 receptor, the Pros can be replaced by some charged amino acids resulting in EC50s similar to those of wild-type receptors, while such substitutions in the nACh receptor ablate function. Ala substitution at one of these Pros also has different effects in the two receptors. Thus, our data show that even highly conserved residues can have distinct behaviors in related Cys-loop receptors.
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Affiliation(s)
- Richard Mosesso
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Dennis A. Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Sarah C. R. Lummis
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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25
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Yong KW, Yuen D, Chen MZ, Porter CJH, Johnston APR. Pointing in the Right Direction: Controlling the Orientation of Proteins on Nanoparticles Improves Targeting Efficiency. Nano Lett 2019; 19:1827-1831. [PMID: 30773887 DOI: 10.1021/acs.nanolett.8b04916] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Protein-conjugated nanoparticles have the potential to precisely deliver therapeutics to target sites in the body by specifically binding to cell surface receptors. To maximize targeting efficiency, the three-dimensional presentation of ligands toward these receptors is crucial. Herein, we demonstrate significantly enhanced targeting of nanoparticles to cancer cells by controlling the protein orientation on the nanoparticle surface. To engineer the point of attachment, we used amber codon reassignment to incorporate a synthetic amino acid, p-azidophenylalanine (azPhe), at specific locations within a single domain antibody (sdAb or nanobody) that recognizes the human epidermal growth factor receptor (EGFR). The azPhe modified sdAb can be tethered to the nanoparticle in a specific orientation using a bioorthogonal click reaction with a strained cyclooctyne. The crystal structure of the sdAb bound to EGFR was used to rationally select sites likely to optimally display the sdAb upon conjugation to a fluorescent nanocrystal (Qdot). Qdots with sdAb attached at the azPhe13 position showed 6 times greater binding affinity to EGFR expressing A549 cells, compared to Qdots with conventionally (succinimidyl ester) conjugated sdAb. As ligand-targeted delivery systems move toward clinical application, this work shows that nanoparticle targeting can be optimized by engineering the site of protein conjugation.
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Affiliation(s)
- Ken W Yong
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , Victoria 3052 , Australia
| | - Daniel Yuen
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , Victoria 3052 , Australia
| | - Moore Z Chen
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , Victoria 3052 , Australia
| | - Christopher J H Porter
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , Victoria 3052 , Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology , Monash University , Parkville , Victoria 3052 , Australia
| | - Angus P R Johnston
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , Victoria 3052 , Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology , Monash University , Parkville , Victoria 3052 , Australia
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26
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Abstract
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Noncanonical
amino acid (ncAA) incorporation has led to significant
advances in protein science and engineering. Traditionally, in vivo incorporation of ncAAs is achieved via amber codon suppression using an engineered orthogonal aminoacyl-tRNA
synthetase:tRNA pair. However, as more complex protein products are
targeted, researchers are identifying additional barriers limiting
the scope of currently available ncAA systems. One barrier is elongation
factor Tu (EF-Tu), a protein responsible for proofreading aa-tRNAs,
which substantially restricts ncAA scope by limiting ncaa-tRNA delivery
to the ribosome. Researchers have responded by engineering ncAA-compatible
EF-Tus for key ncAAs. However, this approach fails to address the
extent to which EF-Tu inhibits efficient ncAA incorporation. Here,
we demonstrate an alternative strategy leveraging computational analysis
to broaden EF-Tu’s substrate specificity. Evolutionary analysis
of EF-Tu and a naturally evolved specialized elongation factor, SelB,
provide the opportunity to engineer EF-Tu by targeting amino acid
residues that are associated with functional divergence between the
two ancient paralogues. Employing amber codon suppression, in combination
with mass spectrometry, we identified two EF-Tu variants with non-native
substrate compatibility. Additionally, we present data showing these
EF-Tu variants contribute to host organismal fitness, working cooperatively
with components of native and engineered translation machinery. These
results demonstrate the viability of our computational method and
lend support to corresponding assumptions about molecular evolution.
This work promotes enhanced polyspecific EF-Tu behavior as a viable
strategy to expand ncAA scope and complements ongoing research emphasizing
the importance of a comprehensive approach to further expand the genetic
code.
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Affiliation(s)
- Vanessa E. DeLey Cox
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Megan F. Cole
- Department of Biology, Emory University, Atlanta, Georgia 30322, United States
| | - Eric A. Gaucher
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
- Department of Biology, Georgia State University, Atlanta, Georgia 30303, United States
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27
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Chen H, Venkat S, McGuire P, Gan Q, Fan C. Recent Development of Genetic Code Expansion for Posttranslational Modification Studies. Molecules 2018; 23:E1662. [PMID: 29986538 PMCID: PMC6100177 DOI: 10.3390/molecules23071662] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 07/03/2018] [Accepted: 07/05/2018] [Indexed: 12/29/2022] Open
Abstract
Nowadays advanced mass spectrometry techniques make the identification of protein posttranslational modifications (PTMs) much easier than ever before. A series of proteomic studies have demonstrated that large numbers of proteins in cells are modified by phosphorylation, acetylation and many other types of PTMs. However, only limited studies have been performed to validate or characterize those identified modification targets, mostly because PTMs are very dynamic, undergoing large changes in different growth stages or conditions. To overcome this issue, the genetic code expansion strategy has been introduced into PTM studies to genetically incorporate modified amino acids directly into desired positions of target proteins. Without using modifying enzymes, the genetic code expansion strategy could generate homogeneously modified proteins, thus providing powerful tools for PTM studies. In this review, we summarized recent development of genetic code expansion in PTM studies for research groups in this field.
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Affiliation(s)
- Hao Chen
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR 72701, USA.
| | - Sumana Venkat
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR 72701, USA.
| | - Paige McGuire
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
| | - Qinglei Gan
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA.
| | - Chenguang Fan
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR 72701, USA.
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA.
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28
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Gordon SE, Munari M, Zagotta WN. Visualizing conformational dynamics of proteins in solution and at the cell membrane. eLife 2018; 7:37248. [PMID: 29923827 PMCID: PMC6056233 DOI: 10.7554/elife.37248] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 06/05/2018] [Indexed: 01/03/2023] Open
Abstract
Conformational dynamics underlie enzyme function, yet are generally inaccessible via traditional structural approaches. FRET has the potential to measure conformational dynamics in vitro and in intact cells, but technical barriers have thus far limited its accuracy, particularly in membrane proteins. Here, we combine amber codon suppression to introduce a donor fluorescent noncanonical amino acid with a new, biocompatible approach for labeling proteins with acceptor transition metals in a method called ACCuRET (Anap Cyclen-Cu2+ resonance energy transfer). We show that ACCuRET measures absolute distances and distance changes with high precision and accuracy using maltose binding protein as a benchmark. Using cell unroofing, we show that ACCuRET can accurately measure rearrangements of proteins in native membranes. Finally, we implement a computational method for correcting the measured distances for the distance distributions observed in proteins. ACCuRET thus provides a flexible, powerful method for measuring conformational dynamics in both soluble proteins and membrane proteins.
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Affiliation(s)
- Sharona E Gordon
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Mika Munari
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - William N Zagotta
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
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29
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Kormos A, Koehler C, Fodor EA, Rutkai ZR, Martin ME, Mező G, Lemke EA, Kele P. Bistetrazine-Cyanines as Double-Clicking Fluorogenic Two-Point Binder or Crosslinker Probes. Chemistry 2018; 24:8841-8847. [PMID: 29676491 DOI: 10.1002/chem.201800910] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Indexed: 12/20/2022]
Abstract
Fluorogenic probes can be used to minimize the background fluorescence of unreacted and nonspecifically adsorbed reagents. The preceding years have brought substantial developments in the design and synthesis of bioorthogonally applicable fluorogenic systems mainly based on the quenching effects of azide and tetrazine moieties. The modulation power exerted by these bioorthogonal motifs typically becomes less efficient on more conjugated systems; that is, on probes with redshifted emission wavelength. To reach efficient quenching, that is, fluorogenicity, even in the red range of the spectrum, we present the synthesis, fluorogenic, and conjugation characterization of bistetrazine-cyanine probes with emission maxima between 600 and 620 nm. The probes can bind to genetically altered proteins harboring an 11-amino acid peptide tag with two appending cyclooctyne motifs. Moreover, we also demonstrate the use of these bistetrazines as fluorogenic, covalent cross-linkers between monocyclooctynylated proteins.
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Affiliation(s)
- Attila Kormos
- Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt. 2., 1117, Budapest, Hungary
| | - Christine Koehler
- Departments of Biology and Chemistry, Pharmacy and Geosciences, Johannes Gutenberg-University Mainz, Johannes-von-Mullerweg 6, 55128, Mainz, Germany.,Institute of Molecular Biology (IMB), Ackermannweg 4, 55128, Mainz, Germany.,EMBL, Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Eszter A Fodor
- Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt. 2., 1117, Budapest, Hungary
| | - Zsófia R Rutkai
- Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt. 2., 1117, Budapest, Hungary
| | - Madison E Martin
- Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt. 2., 1117, Budapest, Hungary
| | - Gábor Mező
- MTA-ELTE Research Group of Peptide Chemistry, Hungarian Academy of Sciences, Pázmány Péter sétány 1a, 1117, Budapest, Hungary
| | - Edward A Lemke
- Departments of Biology and Chemistry, Pharmacy and Geosciences, Johannes Gutenberg-University Mainz, Johannes-von-Mullerweg 6, 55128, Mainz, Germany.,Institute of Molecular Biology (IMB), Ackermannweg 4, 55128, Mainz, Germany.,EMBL, Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Péter Kele
- Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt. 2., 1117, Budapest, Hungary
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30
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Venkat S, Sturges J, Stahman A, Gregory C, Gan Q, Fan C. Genetically Incorporating Two Distinct Post-translational Modifications into One Protein Simultaneously. ACS Synth Biol 2018; 7:689-695. [PMID: 29301074 DOI: 10.1021/acssynbio.7b00408] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Post-translational modifications (PTMs) play important roles in regulating a variety of biological processes. To facilitate PTM studies, the genetic code expansion strategy has been utilized to cotranslationally incorporate individual PTMs such as acetylation and phosphorylation into proteins at specific sites. However, recent studies have demonstrated that PTMs actually work together to regulate protein functions and structures. Thus, simultaneous incorporation of multiple distinct PTMs into one protein is highly desirable. In this study, we utilized the genetic incorporation systems of phosphoserine and acetyllysine to install both phosphorylation and acetylation into target proteins simultaneously in Escherichia coli. And we used this system to study the effect of coexisting acetylation and phosphorylation on malate dehydrogenase, demonstrating a practical application of this system in biochemical studies. Furthermore, we tested the mutual orthogonality of three widely used genetic incorporation systems, indicating the possibility of incorporating three distinct PTMs into one protein simultaneously.
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Affiliation(s)
- Sumana Venkat
- Department
of Chemistry and Biochemistry, ‡Cell and Molecular Biology Program, and §Department of
Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Jourdan Sturges
- Department
of Chemistry and Biochemistry, ‡Cell and Molecular Biology Program, and §Department of
Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Alleigh Stahman
- Department
of Chemistry and Biochemistry, ‡Cell and Molecular Biology Program, and §Department of
Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Caroline Gregory
- Department
of Chemistry and Biochemistry, ‡Cell and Molecular Biology Program, and §Department of
Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Qinglei Gan
- Department
of Chemistry and Biochemistry, ‡Cell and Molecular Biology Program, and §Department of
Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Chenguang Fan
- Department
of Chemistry and Biochemistry, ‡Cell and Molecular Biology Program, and §Department of
Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, United States
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31
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Thomas EE, Pandey N, Knudsen S, Ball ZT, Silberg JJ. Programming Post-Translational Control over the Metabolic Labeling of Cellular Proteins with a Noncanonical Amino Acid. ACS Synth Biol 2017; 6:1572-1583. [PMID: 28419802 DOI: 10.1021/acssynbio.7b00100] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Transcriptional control can be used to program cells to label proteins with noncanonical amino acids by regulating the expression of orthogonal aminoacyl tRNA synthetases (aaRSs). However, we cannot yet program cells to control labeling in response to aaRS and ligand binding. To identify aaRSs whose activities can be regulated by interactions with ligands, we used a combinatorial approach to discover fragmented variants of Escherichia coli methionyl tRNA synthetase (MetRS) that require fusion to associating proteins for maximal activity. We found that these split proteins could be leveraged to create ligand-dependent MetRS using two approaches. When a pair of MetRS fragments was fused to FKBP12 and the FKBP-rapamycin binding domain (FRB) of mTOR and mutations were introduced that direct substrate specificity toward azidonorleucine (Anl), Anl metabolic labeling was significantly enhanced in growth medium containing rapamycin, which stabilizes the FKBP12-FRB complex. In addition, fusion of MetRS fragments to the termini of the ligand-binding domain of the estrogen receptor yielded proteins whose Anl metabolic labeling was significantly enhanced when 4-hydroxytamoxifen (4-HT) was added to the growth medium. These findings suggest that split MetRS can be fused to a range of ligand-binding proteins to create aaRSs whose metabolic labeling activities depend upon post-translational interactions with ligands.
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Affiliation(s)
- Emily E. Thomas
- Department
of Biosciences, ‡Biochemistry and Cell Biology Graduate Program, §Department of Chemistry, ∥Department of Bioengineering, Rice University, Houston, Texas 77005, United States
| | - Naresh Pandey
- Department
of Biosciences, ‡Biochemistry and Cell Biology Graduate Program, §Department of Chemistry, ∥Department of Bioengineering, Rice University, Houston, Texas 77005, United States
| | - Sarah Knudsen
- Department
of Biosciences, ‡Biochemistry and Cell Biology Graduate Program, §Department of Chemistry, ∥Department of Bioengineering, Rice University, Houston, Texas 77005, United States
| | - Zachary T. Ball
- Department
of Biosciences, ‡Biochemistry and Cell Biology Graduate Program, §Department of Chemistry, ∥Department of Bioengineering, Rice University, Houston, Texas 77005, United States
| | - Jonathan J. Silberg
- Department
of Biosciences, ‡Biochemistry and Cell Biology Graduate Program, §Department of Chemistry, ∥Department of Bioengineering, Rice University, Houston, Texas 77005, United States
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32
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Abstract
EAG-like (ELK) voltage-gated potassium channels are abundantly expressed in the brain. These channels exhibit a behavior called voltage-dependent potentiation (VDP), which appears to be a specialization to dampen the hyperexitability of neurons. VDP manifests as a potentiation of current amplitude, hyperpolarizing shift in voltage sensitivity, and slowing of deactivation in response to a depolarizing prepulse. Here we show that VDP of D. rerio ELK channels involves the structural interaction between the intracellular N-terminal eag domain and C-terminal CNBHD. Combining transition metal ion FRET, patch-clamp fluorometry, and incorporation of a fluorescent noncanonical amino acid, we show that there is a rearrangement in the eag domain-CNBHD interaction with the kinetics, voltage-dependence, and ATP-dependence of VDP. We propose that the activation of ELK channels involves a slow open-state dependent rearrangement of the direct interaction between the eag domain and CNBHD, which stabilizes the opening of the channel. DOI:http://dx.doi.org/10.7554/eLife.26355.001 In humans and other animals, electrical signals trigger the heart to beat and carry information around the brain and nervous system. Particular cells can generate these signals by regulating the flow of ions into and out of the cell via proteins called ion channels. These proteins sit in the membrane that surrounds the cell and will open or close in response to specific signals. For example, an ion channel in humans called hERG allows positively-charged potassium ions to flow out of a heart cell to help the cell return to its “resting” state after producing an electrical signal. Defects in hERG can alter the rhythm at which the heart beats, leading to a serious condition called Long QT syndrome. The human hERG channel is part of a family of related channels known as the KCNH channels. These channels are made of four protein subunits that assemble to form a pore that spans the cell membrane. When a cell is resting before producing an electrical signal, KCNH channels are generally closed. However, once an electrical signal starts, the flow of ions through other ion channels in the cell membrane changes an electrical property across the membrane known as the “voltage”. This change in voltage causes KCNH channels to open. Dai and Zagotta studied how a KCNH channel known as ELK from zebrafish responds to changes in membrane voltage. The experiments show that the manner in which ELK channels respond to the voltage is due to changes in how the subunits interact in the part of the channel that lies inside the cell. Further experiments using several new techniques reveal in much more detail how the shape of the channel alters as the voltage changes. These new techniques could also be used to observe how other KCNH channels in the heart and brain change shape in response to changes in voltage. This could lead to the design of new drugs to treat heart and neurological diseases. DOI:http://dx.doi.org/10.7554/eLife.26355.002
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Affiliation(s)
- Gucan Dai
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - William N Zagotta
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
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33
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Kipper K, Lundius EG, Ćurić V, Nikić I, Wiessler M, Lemke EA, Elf J. Application of Noncanonical Amino Acids for Protein Labeling in a Genomically Recoded Escherichia coli. ACS Synth Biol 2017; 6:233-255. [PMID: 27775882 DOI: 10.1021/acssynbio.6b00138] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Small synthetic fluorophores are in many ways superior to fluorescent proteins as labels for imaging. A major challenge is to use them for a protein-specific labeling in living cells. Here, we report on our use of noncanonical amino acids that are genetically encoded via the pyrrolysyl-tRNA/pyrrolysyl-RNA synthetase pair at artificially introduced TAG codons in a recoded E. coli strain. The strain is lacking endogenous TAG codons and the TAG-specific release factor RF1. The amino acids contain bioorthogonal groups that can be clicked to externally supplied dyes, thus enabling protein-specific labeling in live cells. We find that the noncanonical amino acid incorporation into the target protein is robust for diverse amino acids and that the usefulness of the recoded E. coli strain mainly derives from the absence of release factor RF1. However, the membrane permeable dyes display high nonspecific binding in intracellular environment and the electroporation of hydrophilic nonmembrane permeable dyes severely impairs growth of the recoded strain. In contrast, proteins exposed on the outer membrane of E. coli can be labeled with hydrophilic dyes with a high specificity as demonstrated by labeling of the osmoporin OmpC. Here, labeling can be made sufficiently specific to enable single molecule studies as exemplified by OmpC single particle tracking.
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Affiliation(s)
- Kalle Kipper
- Department
of Molecular and Cell Biology, Science for Life Laboratory, Uppsala University, Se-751 24 Uppsala, Sweden
| | - Ebba G. Lundius
- Department
of Molecular and Cell Biology, Science for Life Laboratory, Uppsala University, Se-751 24 Uppsala, Sweden
| | - Vladimir Ćurić
- Department
of Molecular and Cell Biology, Science for Life Laboratory, Uppsala University, Se-751 24 Uppsala, Sweden
| | - Ivana Nikić
- Structural
and Computational Biology Unit, Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, 69117, Germany
| | - Manfred Wiessler
- Biological
Chemistry, Deutsche Krebsforschungszentrum, Heidelberg, 69120, Germany
| | - Edward A. Lemke
- Structural
and Computational Biology Unit, Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, 69117, Germany
| | - Johan Elf
- Department
of Molecular and Cell Biology, Science for Life Laboratory, Uppsala University, Se-751 24 Uppsala, Sweden
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34
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Gan R, Perez JG, Carlson ED, Ntai I, Isaacs FJ, Kelleher NL, Jewett MC. Translation system engineering in Escherichia coli enhances non-canonical amino acid incorporation into proteins. Biotechnol Bioeng 2017; 114:1074-1086. [PMID: 27987323 DOI: 10.1002/bit.26239] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 10/28/2016] [Accepted: 12/13/2016] [Indexed: 01/15/2023]
Abstract
The ability to site-specifically incorporate non-canonical amino acids (ncAAs) into proteins has made possible the study of protein structure and function in fundamentally new ways, as well as the bio synthesis of unnatural polymers. However, the task of site-specifically incorporating multiple ncAAs into proteins with high purity and yield continues to present a challenge. At the heart of this challenge lies the lower efficiency of engineered orthogonal translation system components compared to their natural counterparts (e.g., translation elements that specifically use a ncAA and do not interact with the cell's natural translation apparatus). Here, we show that evolving and tuning expression levels of multiple components of an engineered translation system together as a whole enhances ncAA incorporation efficiency. Specifically, we increase protein yield when incorporating multiple p-azido-phenylalanine(pAzF) residues into proteins by (i) evolving the Methanocaldococcus jannaschii p-azido-phenylalanyl-tRNA synthetase anti-codon binding domain, (ii) evolving the elongation factor Tu amino acid-binding pocket, and (iii) tuning the expression of evolved translation machinery components in a single vector. Use of the evolved translation machinery in a genomically recoded organism lacking release factor one enabled enhanced multi-site ncAA incorporation into proteins. We anticipate that our approach to orthogonal translation system development will accelerate and expand our ability to site-specifically incorporate multiple ncAAs into proteins and biopolymers, advancing new horizons for synthetic and chemical biotechnology. Biotechnol. Bioeng. 2017;114: 1074-1086. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Rui Gan
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208-3120
| | - Jessica G Perez
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208-3120
| | - Erik D Carlson
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208-3120
| | - Ioanna Ntai
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208-3120.,Chemistry of Life Processes Institute, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208
| | - Farren J Isaacs
- Systems Biology Institute, Yale University, West Haven, Connecticut.,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut
| | - Neil L Kelleher
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208-3120.,Chemistry of Life Processes Institute, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208.,Department of Molecular Biosciences, Northwestern University, Evanston, Illinois
| | - Michael C Jewett
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208-3120.,Chemistry of Life Processes Institute, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208.,Interdisciplinary Biological Sciences Program, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208-0001.,Northwestern Institute on Complex Systems, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208.,Simpson Querry Institute, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208
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35
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Monk JW, Leonard SP, Brown CW, Hammerling MJ, Mortensen C, Gutierrez AE, Shin NY, Watkins E, Mishler DM, Barrick JE. Rapid and Inexpensive Evaluation of Nonstandard Amino Acid Incorporation in Escherichia coli. ACS Synth Biol 2017; 6:45-54. [PMID: 27648665 DOI: 10.1021/acssynbio.6b00192] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
By introducing engineered tRNA and aminoacyl-tRNA synthetase pairs into an organism, its genetic code can be expanded to incorporate nonstandard amino acids (nsAAs). The performance of these orthogonal translation systems (OTSs) varies greatly, however, with respect to the efficiency and accuracy of decoding a reassigned codon as the nsAA. To enable rapid and systematic comparisons of these critical parameters, we developed a toolkit for characterizing any Escherichia coli OTS that reassigns the amber stop codon (TAG). It assesses OTS performance by comparing how the fluorescence of strains carrying plasmids encoding a fused RFP-GFP reading frame, either with or without an intervening TAG codon, depends on the presence of the nsAA. We used this kit to (1) examine nsAA incorporation by seven different OTSs, (2) optimize nsAA concentration in growth media, (3) define the polyspecificity of an OTS, and (4) characterize evolved variants of amberless E. coli with improved growth rates.
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Affiliation(s)
- Jordan W. Monk
- Center for Systems and Synthetic
Biology, Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Sean P. Leonard
- Center for Systems and Synthetic
Biology, Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Colin W. Brown
- Center for Systems and Synthetic
Biology, Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Michael J. Hammerling
- Center for Systems and Synthetic
Biology, Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Catherine Mortensen
- Center for Systems and Synthetic
Biology, Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Alejandro E. Gutierrez
- Center for Systems and Synthetic
Biology, Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Nathan Y. Shin
- Center for Systems and Synthetic
Biology, Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Ella Watkins
- Center for Systems and Synthetic
Biology, Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Dennis M. Mishler
- Center for Systems and Synthetic
Biology, Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Jeffrey E. Barrick
- Center for Systems and Synthetic
Biology, Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
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Luo X, Zambaldo C, Liu T, Zhang Y, Xuan W, Wang C, Reed SA, Yang PY, Wang RE, Javahishvili T, Schultz PG, Young TS. Recombinant thiopeptides containing noncanonical amino acids. Proc Natl Acad Sci U S A 2016; 113:3615-20. [PMID: 26976568 DOI: 10.1073/pnas.1602733113] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Thiopeptides are a subclass of ribosomally synthesized and posttranslationally modified peptides (RiPPs) with complex molecular architectures and an array of biological activities, including potent antimicrobial activity. Here we report the generation of thiopeptides containing noncanonical amino acids (ncAAs) by introducing orthogonal amber suppressor aminoacyl-tRNA synthetase/tRNA pairs into a thiocillin producer strain of Bacillus cereus .We demonstrate that thiopeptide variants containing ncAAs with bioorthogonal chemical reactivity can be further postbiosynthetically modified with biophysical probes, including fluorophores and photo-cross-linkers. This work allows the site-specific incorporation of ncAAs into thiopeptides to increase their structural diversity and probe their biological activity; similar approaches can likely be applied to other classes of RiPPs.
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Exner MP, Köhling S, Rivollier J, Gosling S, Srivastava P, Palyancheva ZI, Herdewijn P, Heck MP, Rademann J, Budisa N. Incorporation of Amino Acids with Long-Chain Terminal Olefins into Proteins. Molecules 2016; 21:287. [PMID: 26938510 PMCID: PMC6272937 DOI: 10.3390/molecules21030287] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 02/23/2016] [Accepted: 02/25/2016] [Indexed: 01/05/2023] Open
Abstract
The increasing need for site-specific protein decorations that mimic natural posttranslational modifications requires access to a variety of noncanonical amino acids with moieties enabling bioorthogonal conjugation chemistry. Here we present the incorporation of long-chain olefinic amino acids into model proteins with rational variants of pyrrolysyl-tRNA synthetase (PylRS). Nε-heptenoyl lysine was incorporated for the first time using the known promiscuous variant PylRS(Y306A/Y384F), and Nε-pentenoyl lysine was incorporated in significant yields with the novel variant PylRS(C348A/Y384F). This is the only example of rational modification at position C348 to enlarge the enzyme's binding pocket. Furthermore, we demonstrate the feasibility of our chosen amino acids in the thiol-ene conjugation reaction with a thiolated polysaccharide.
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Affiliation(s)
- Matthias P Exner
- Institute of Chemistry, Technische Universität Berlin, Mueller-Breslau-Strasse 10, 10623 Berlin, Germany.
| | - Sebastian Köhling
- Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2+4, 14195 Berlin, Germany.
| | - Julie Rivollier
- Service de Chimie Bioorganique et de Marquage, iBiTecS, CEA, 91191 Gif-sur-Yvette, France.
| | - Sandrine Gosling
- Service de Chimie Bioorganique et de Marquage, iBiTecS, CEA, 91191 Gif-sur-Yvette, France.
| | - Puneet Srivastava
- Medicinal Chemistry, Rega Institute for Medical Research, KU Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium.
| | - Zheni I Palyancheva
- Institute of Chemistry, Technische Universität Berlin, Mueller-Breslau-Strasse 10, 10623 Berlin, Germany.
| | - Piet Herdewijn
- Medicinal Chemistry, Rega Institute for Medical Research, KU Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium.
| | - Marie-Pierre Heck
- Service de Chimie Bioorganique et de Marquage, iBiTecS, CEA, 91191 Gif-sur-Yvette, France.
| | - Jörg Rademann
- Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2+4, 14195 Berlin, Germany.
| | - Nediljko Budisa
- Institute of Chemistry, Technische Universität Berlin, Mueller-Breslau-Strasse 10, 10623 Berlin, Germany.
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Buller AR, Brinkmann-Chen S, Romney DK, Herger M, Murciano-Calles J, Arnold FH. Directed evolution of the tryptophan synthase β-subunit for stand-alone function recapitulates allosteric activation. Proc Natl Acad Sci U S A 2015; 112:14599-604. [PMID: 26553994 DOI: 10.1073/pnas.1516401112] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Enzymes in heteromeric, allosterically regulated complexes catalyze a rich array of chemical reactions. Separating the subunits of such complexes, however, often severely attenuates their catalytic activities, because they can no longer be activated by their protein partners. We used directed evolution to explore allosteric regulation as a source of latent catalytic potential using the β-subunit of tryptophan synthase from Pyrococcus furiosus (PfTrpB). As part of its native αββα complex, TrpB efficiently produces tryptophan and tryptophan analogs; activity drops considerably when it is used as a stand-alone catalyst without the α-subunit. Kinetic, spectroscopic, and X-ray crystallographic data show that this lost activity can be recovered by mutations that reproduce the effects of complexation with the α-subunit. The engineered PfTrpB is a powerful platform for production of Trp analogs and for further directed evolution to expand substrate and reaction scope.
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Xiao H, Nasertorabi F, Choi SH, Han GW, Reed SA, Stevens RC, Schultz PG. Exploring the potential impact of an expanded genetic code on protein function. Proc Natl Acad Sci U S A 2015; 112:6961-6. [PMID: 26038548 DOI: 10.1073/pnas.1507741112] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
With few exceptions, all living organisms encode the same 20 canonical amino acids; however, it remains an open question whether organisms with additional amino acids beyond the common 20 might have an evolutionary advantage. Here, we begin to test that notion by making a large library of mutant enzymes in which 10 structurally distinct noncanonical amino acids were substituted at single sites randomly throughout TEM-1 β-lactamase. A screen for growth on the β-lactam antibiotic cephalexin afforded a unique p-acrylamido-phenylalanine (AcrF) mutation at Val-216 that leads to an increase in catalytic efficiency by increasing kcat, but not significantly affecting KM. To understand the structural basis for this enhanced activity, we solved the X-ray crystal structures of the ligand-free mutant enzyme and of the deacylation-defective wild-type and mutant cephalexin acyl-enzyme intermediates. These structures show that the Val-216-AcrF mutation leads to conformational changes in key active site residues-both in the free enzyme and upon formation of the acyl-enzyme intermediate-that lower the free energy of activation of the substrate transacylation reaction. The functional changes induced by this mutation could not be reproduced by substitution of any of the 20 canonical amino acids for Val-216, indicating that an expanded genetic code may offer novel solutions to proteins as they evolve new activities.
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