1
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Srinivasan K, Erramilli SK, Chakravarthy S, Gonzalez A, Kossiakoff A, Noinaj N. Characterization of synthetic antigen binding fragments targeting Toc75 for the isolation of TOC in A. thaliana and P. sativum. Structure 2023; 31:595-606.e5. [PMID: 36977410 PMCID: PMC10164082 DOI: 10.1016/j.str.2023.03.002] [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: 07/15/2022] [Revised: 12/21/2022] [Accepted: 03/02/2023] [Indexed: 03/29/2023]
Abstract
Roughly 95% of the proteins that make up the chloroplast must be imported from the cytoplasm. The machinery responsible for the translocation of these cargo proteins is called the translocon at the outer membrane of chloroplast (TOC). The TOC core consists of three proteins, Toc34, Toc75, and Toc159; no high-resolution structure has been solved of fully assembled TOC from plants. Efforts toward determining the structure of the TOC have been hindered almost entirely by difficulties in producing sufficient yields for structural studies. In this study, we introduce an innovative method that utilizes synthetic antigen binding fragments (sABs) to isolate TOC directly from wild-type plant biomass including A. thaliana and P. sativum. Binding between the sABs and the POTRA domains was characterized by size-exclusion chromatography coupled with small-angle X-ray scattering (SEC-SAXS), X-ray crystallography, and isothermal titration calorimetry. We also demonstrate the isolation of the TOC from P. sativum, laying the framework for large-scale isolation and purification of TOC for functional and structural studies.
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Affiliation(s)
- Karthik Srinivasan
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Satchal K Erramilli
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Srinivas Chakravarthy
- The Biophysics Collaborative Access Team (BioCAT), Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Adrian Gonzalez
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Anthony Kossiakoff
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Nicholas Noinaj
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.
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2
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Garland‐Kuntz E, Samassekou K, Fisher I, Muralidharan K, Everly A, Emmerson L, Reyes J, Erramilli S, Kossiakoff A, Lyon A. Structural Insights into Phospholipase Cε. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r3961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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3
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Enderle L, Shalaby KH, Gorelik M, Weiss A, Blazer LL, Paduch M, Cardarelli L, Kossiakoff A, Adams JJ, Sidhu SS. A T cell redirection platform for co-targeting dual antigens on solid tumors. MAbs 2021; 13:1933690. [PMID: 34190031 PMCID: PMC8253144 DOI: 10.1080/19420862.2021.1933690] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
In order to direct T cells to specific features of solid cancer cells, we engineered a bispecific antibody format, named Dual Antigen T cell Engager (DATE), by fusing a single-chain variable fragment targeting CD3 to a tumor-targeting antigen-binding fragment. In this format, multiple novel paratopes against different tumor antigens were able to recruit T-cell cytotoxicity to tumor cells in vitro and in an in vivo pancreatic ductal adenocarcinoma xenograft model. Since unique surface antigens in solid tumors are limited, in order to enhance selectivity, we further engineered “double-DATEs” targeting two tumor antigens simultaneously. The double-DATE contains an additional autonomous variable heavy-chain domain, which binds a second tumor antigen without itself eliciting a cytotoxic response. This novel modality provides a strategy to enhance the selectivity of immune redirection through binary targeting of native tumor antigens. The modularity and use of a common, stable human framework for all components enables a pipeline approach to rapidly develop a broad repertoire of tailored DATEs and double-DATEs with favorable biophysical properties and high potencies and selectivities.
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Affiliation(s)
- Leonie Enderle
- Donnelly Centre, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Karim H Shalaby
- Donnelly Centre, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Maryna Gorelik
- Donnelly Centre, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Alexander Weiss
- Donnelly Centre, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Levi L Blazer
- Donnelly Centre, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Marcin Paduch
- Institute for Biophysical Dynamics, Gordon Center for Integrative Science, Chicago, USA
| | - Lia Cardarelli
- Donnelly Centre, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Anthony Kossiakoff
- Institute for Biophysical Dynamics, Gordon Center for Integrative Science, Chicago, USA.,Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, USA
| | - Jarrett J Adams
- Donnelly Centre, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Sachdev S Sidhu
- Donnelly Centre, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
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4
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Garland E, Rugema N, Sieng M, Muralidharan K, Fisher I, Everly A, Erramilli S, Van Camp M, Emmerson L, Reyes J, Kossiakoff A, Lyon A. Structural Insights into PLCε: Discovery of an Integrated RA1 Domain and Novel Regulatory Elements. FASEB J 2021. [DOI: 10.1096/fasebj.2021.35.s1.03032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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5
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Chen Q, Plasencia M, Li Z, Mukherjee S, Patra D, Chen C, Klose T, Yao X, Kossiakoff A, Chang L, Andrews P, Tesmer J. Structure of the rhodopsin–rhodopsin kinase complex defines the rules of engagement between G protein‐coupled receptors (GPCRs) and GPCR kinases. FASEB J 2021. [DOI: 10.1096/fasebj.2021.35.s1.03635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Zhuang Li
- Biological SciencesPurdue UniversityWest LafayetteIN
| | | | | | | | | | | | | | - Leifu Chang
- Biological SciencesPurdue UniversityWest LafayetteIN
| | | | - John Tesmer
- Biological Sciences and of Medicinal Chemistry and Molecular PharmacologyPurdue UniversityWest LafayetteIN
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6
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Farcasanu M, Wang AG, Uchański T, Bailey LJ, Yue J, Chen Z, Wu X, Kossiakoff A, Tang WJ. Rapid Discovery and Characterization of Synthetic Neutralizing Antibodies against Anthrax Edema Toxin. Biochemistry 2019; 58:2996-3004. [PMID: 31243996 DOI: 10.1021/acs.biochem.9b00184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Anthrax, a lethal, weaponizable disease caused by Bacillus anthracis, acts through exotoxins that are primary mediators of systemic toxicity and also targets for neutralization by passive immunotherapy. The ease of engineering B. anthracis strains resistant to established therapy and the historic use of the microbe in bioterrorism present a compelling test case for platforms that permit the rapid and modular development of neutralizing agents. In vitro antigen-binding fragment (Fab) selection offers the advantages of speed, sequence level molecular control, and engineering flexibility compared to traditional monoclonal antibody pipelines. By screening an unbiased, chemically synthetic phage Fab library and characterizing hits in cell-based assays, we identified two high-affinity neutralizing Fabs, A4 and B7, against anthrax edema factor (EF), a key mediator of anthrax pathogenesis. Engineered homodimers of these Fabs exhibited potency comparable to that of the best reported neutralizing monoclonal antibody against EF at preventing EF-induced cyclic AMP production. Using internalization assays in COS cells, B7 was found to block steps prior to EF internalization. This work demonstrates the efficacy of synthetic alternatives to traditional antibody therapeutics against anthrax while also demonstrating a broadly generalizable, rapid, and modular screening pipeline for neutralizing antibody generation.
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Affiliation(s)
- Mara Farcasanu
- The Ben May Department for Cancer Research , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Andrew G Wang
- The Ben May Department for Cancer Research , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Tomasz Uchański
- Department of Biochemistry and Molecular Biology , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Lucas J Bailey
- Department of Biochemistry and Molecular Biology , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Jiping Yue
- The Ben May Department for Cancer Research , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Zhaochun Chen
- National Institute of Allergy and Infection , National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Xiaoyang Wu
- The Ben May Department for Cancer Research , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Anthony Kossiakoff
- Department of Biochemistry and Molecular Biology , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Wei-Jen Tang
- The Ben May Department for Cancer Research , The University of Chicago , Chicago , Illinois 60637 , United States
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7
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Hornsby M, Paduch M, Miersch S, Sääf A, Matsuguchi T, Lee B, Wypisniak K, Doak A, King D, Usatyuk S, Perry K, Lu V, Thomas W, Luke J, Goodman J, Hoey RJ, Lai D, Griffin C, Li Z, Vizeacoumar FJ, Dong D, Campbell E, Anderson S, Zhong N, Gräslund S, Koide S, Moffat J, Sidhu S, Kossiakoff A, Wells J. A High Through-put Platform for Recombinant Antibodies to Folded Proteins. Mol Cell Proteomics 2015; 14:2833-47. [PMID: 26290498 PMCID: PMC4597156 DOI: 10.1074/mcp.o115.052209] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Indexed: 01/09/2023] Open
Abstract
Antibodies are key reagents in biology and medicine, but commercial sources are rarely recombinant and thus do not provide a permanent and renewable resource. Here, we describe an industrialized platform to generate antigens and validated recombinant antibodies for 346 transcription factors (TFs) and 211 epigenetic antigens. We describe an optimized automated phage display and antigen expression pipeline that in aggregate produced about 3000 sequenced Fragment antigen-binding domain that had high affinity (typically EC50<20 nm), high stability (Tm∼80 °C), good expression in E. coli (∼5 mg/L), and ability to bind antigen in complex cell lysates. We evaluated a subset of Fabs generated to homologous SCAN domains for binding specificities. These Fragment antigen-binding domains were monospecific to their target SCAN antigen except in rare cases where they cross-reacted with a few highly related antigens. Remarkably, immunofluorescence experiments in six cell lines for 270 of the TF antigens, each having multiple antibodies, show that ∼70% stain predominantly in the cytosol and ∼20% stain in the nucleus which reinforces the dominant role that translocation plays in TF biology. These cloned antibody reagents are being made available to the academic community through our web site recombinant-antibodies.org to allow a more system-wide analysis of TF and chromatin biology. We believe these platforms, infrastructure, and automated approaches will facilitate the next generation of renewable antibody reagents to the human proteome in the coming decade.
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Affiliation(s)
- Michael Hornsby
- From the ‡Department of Pharmaceutical Chemistry University of California, San Francisco, California 94158
| | - Marcin Paduch
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Shane Miersch
- ¶Donnelly Center for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, MG5 1L6, Canada
| | - Annika Sääf
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Tet Matsuguchi
- From the ‡Department of Pharmaceutical Chemistry University of California, San Francisco, California 94158
| | - Brian Lee
- From the ‡Department of Pharmaceutical Chemistry University of California, San Francisco, California 94158
| | - Karolina Wypisniak
- From the ‡Department of Pharmaceutical Chemistry University of California, San Francisco, California 94158
| | - Allison Doak
- From the ‡Department of Pharmaceutical Chemistry University of California, San Francisco, California 94158
| | - Daniel King
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Svitlana Usatyuk
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Kimberly Perry
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Vince Lu
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - William Thomas
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Judy Luke
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Jay Goodman
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Robert J Hoey
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Darson Lai
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Carly Griffin
- ¶Donnelly Center for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, MG5 1L6, Canada
| | - Zhijian Li
- ¶Donnelly Center for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, MG5 1L6, Canada
| | - Franco J Vizeacoumar
- **Saskatchewan Cancer Agency, University of Saskatchewan, Saskatoon, S7N 4H4, Canada
| | - Debbie Dong
- ¶Donnelly Center for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, MG5 1L6, Canada
| | - Elliot Campbell
- ‖Center for Advanced Biotechnology and Medicine, Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854
| | - Stephen Anderson
- ‖Center for Advanced Biotechnology and Medicine, Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854
| | - Nan Zhong
- ‡‡Structural Genomics Consortium, Toronto, M5G Il7, Canada
| | | | - Shohei Koide
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
| | - Jason Moffat
- ¶Donnelly Center for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, MG5 1L6, Canada
| | - Sachdev Sidhu
- ¶Donnelly Center for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, MG5 1L6, Canada;
| | - Anthony Kossiakoff
- §Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| | - James Wells
- From the ‡Department of Pharmaceutical Chemistry University of California, San Francisco, California 94158;
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8
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Griffin C, Miersch S, Marcon E, Banerjee S, Wells J, Hornsby M, Kossiakoff A, Koide S, Paduch M, Sidhu S, Moffat J. Validation of Recombinant Antibodies Against Human Transcription Factors. FASEB J 2015. [DOI: 10.1096/fasebj.29.1_supplement.571.13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Carly Griffin
- Donnelly Centre University of TorontoTorontoOntarioCanada
| | - Shane Miersch
- Donnelly Centre University of TorontoTorontoOntarioCanada
| | - Edyta Marcon
- Donnelly Centre University of TorontoTorontoOntarioCanada
| | | | - Jim Wells
- Pharmaceutical Chemistry University of California San FranciscoSan FranciscoCaliforniaUnited States
| | - Michael Hornsby
- Pharmaceutical Chemistry University of California San FranciscoSan FranciscoCaliforniaUnited States
| | - Anthony Kossiakoff
- Biochemistry and Molecular BiologyUniversity of ChicagoChicagoIllinoisUnited States
| | - Shohei Koide
- Biochemistry and Molecular BiologyUniversity of ChicagoChicagoIllinoisUnited States
| | - Marcin Paduch
- Biochemistry and Molecular BiologyUniversity of ChicagoChicagoIllinoisUnited States
| | - Sachdev Sidhu
- Donnelly Centre University of TorontoTorontoOntarioCanada
| | - Jason Moffat
- Donnelly Centre University of TorontoTorontoOntarioCanada
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9
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Miersch S, Li Z, Hanna R, McLaughlin ME, Hornsby M, Matsuguchi T, Paduch M, Sääf A, Wells J, Koide S, Kossiakoff A, Sidhu SS. Scalable high throughput selection from phage-displayed synthetic antibody libraries. J Vis Exp 2015:51492. [PMID: 25651360 DOI: 10.3791/51492] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The demand for antibodies that fulfill the needs of both basic and clinical research applications is high and will dramatically increase in the future. However, it is apparent that traditional monoclonal technologies are not alone up to this task. This has led to the development of alternate methods to satisfy the demand for high quality and renewable affinity reagents to all accessible elements of the proteome. Toward this end, high throughput methods for conducting selections from phage-displayed synthetic antibody libraries have been devised for applications involving diverse antigens and optimized for rapid throughput and success. Herein, a protocol is described in detail that illustrates with video demonstration the parallel selection of Fab-phage clones from high diversity libraries against hundreds of targets using either a manual 96 channel liquid handler or automated robotics system. Using this protocol, a single user can generate hundreds of antigens, select antibodies to them in parallel and validate antibody binding within 6-8 weeks. Highlighted are: i) a viable antigen format, ii) pre-selection antigen characterization, iii) critical steps that influence the selection of specific and high affinity clones, and iv) ways of monitoring selection effectiveness and early stage antibody clone characterization. With this approach, we have obtained synthetic antibody fragments (Fabs) to many target classes including single-pass membrane receptors, secreted protein hormones, and multi-domain intracellular proteins. These fragments are readily converted to full-length antibodies and have been validated to exhibit high affinity and specificity. Further, they have been demonstrated to be functional in a variety of standard immunoassays including Western blotting, ELISA, cellular immunofluorescence, immunoprecipitation and related assays. This methodology will accelerate antibody discovery and ultimately bring us closer to realizing the goal of generating renewable, high quality antibodies to the proteome.
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Affiliation(s)
- Shane Miersch
- The Recombinant Antibody Network; The Banting and Best Department of Medical Research, University of Toronto;
| | - Zhijian Li
- The Recombinant Antibody Network; The Banting and Best Department of Medical Research, University of Toronto
| | - Rachel Hanna
- The Recombinant Antibody Network; The Banting and Best Department of Medical Research, University of Toronto
| | - Megan E McLaughlin
- The Recombinant Antibody Network; The Banting and Best Department of Medical Research, University of Toronto
| | - Michael Hornsby
- The Recombinant Antibody Network; Antibiome Center, University of California, San Francisco at Mission Bay
| | - Tet Matsuguchi
- The Recombinant Antibody Network; Antibiome Center, University of California, San Francisco at Mission Bay
| | - Marcin Paduch
- The Recombinant Antibody Network; Department of Biochemistry and Molecular Biology, The University of Chicago
| | - Annika Sääf
- The Recombinant Antibody Network; Department of Biochemistry and Molecular Biology, The University of Chicago
| | - Jim Wells
- The Recombinant Antibody Network; Antibiome Center, University of California, San Francisco at Mission Bay
| | - Shohei Koide
- The Recombinant Antibody Network; Department of Biochemistry and Molecular Biology, The University of Chicago
| | - Anthony Kossiakoff
- The Recombinant Antibody Network; Department of Biochemistry and Molecular Biology, The University of Chicago
| | - Sachdev S Sidhu
- The Recombinant Antibody Network; The Banting and Best Department of Medical Research, University of Toronto
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10
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Li Q, Wanderling S, Paduch M, Medovoy D, Singharoy A, McGreevy R, Villalba-Galea CA, Hulse RE, Roux B, Schulten K, Kossiakoff A, Perozo E. Structural mechanism of voltage-dependent gating in an isolated voltage-sensing domain. Nat Struct Mol Biol 2014; 21:244-52. [PMID: 24487958 DOI: 10.1038/nsmb.2768] [Citation(s) in RCA: 188] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 01/10/2014] [Indexed: 01/26/2023]
Abstract
The transduction of transmembrane electric fields into protein motion has an essential role in the generation and propagation of cellular signals. Voltage-sensing domains (VSDs) carry out these functions through reorientations of positive charges in the S4 helix. Here, we determined crystal structures of the Ciona intestinalis VSD (Ci-VSD) in putatively active and resting conformations. S4 undergoes an ~5-Å displacement along its main axis, accompanied by an ~60° rotation. This movement is stabilized by an exchange in countercharge partners in helices S1 and S3 that generates an estimated net charge transfer of ~1 eo. Gating charges move relative to a ''hydrophobic gasket' that electrically divides intra- and extracellular compartments. EPR spectroscopy confirms the limited nature of S4 movement in a membrane environment. These results provide an explicit mechanism for voltage sensing and set the basis for electromechanical coupling in voltage-dependent enzymes and ion channels.
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Affiliation(s)
- Qufei Li
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - Sherry Wanderling
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - Marcin Paduch
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - David Medovoy
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - Abhishek Singharoy
- Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Ryan McGreevy
- Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Carlos A Villalba-Galea
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - Raymond E Hulse
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - Benoît Roux
- 1] Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA. [2] Institute of Biophysical Dynamics, University of Chicago, Chicago, Illinois, USA
| | - Klaus Schulten
- 1] Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA. [2] Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Anthony Kossiakoff
- 1] Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA. [2] Institute of Biophysical Dynamics, University of Chicago, Chicago, Illinois, USA
| | - Eduardo Perozo
- 1] Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA. [2] Institute of Biophysical Dynamics, University of Chicago, Chicago, Illinois, USA
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11
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Li Q, Wanderling S, Paduch M, Medovoy D, Villalba-Galea C, Hulse R, Roux B, Kossiakoff A, Perozo E. Structural Mechanism of Voltage-Dependent Gating in an Isolated Voltage-Sensing Domain. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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12
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Brawley CM, Uysal S, Rizk S, Luchniak A, Kossiakoff A, Rock RS. Generation of a De Novo Actin Pointed-End Binding Protein. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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13
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Uysal S, Cuello LG, Jogini V, Cortes DM, Koide S, Perozo E, Kossiakoff A. Crystal Structure Of Full-length Kcsa Trapped In Open Conformation Reveals That C-terminal Domain Fine Tunes Activation And Coupled Inactivation. Biophys J 2009. [DOI: 10.1016/j.bpj.2008.12.1994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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14
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Qiu Y, Zhang R, Binkowski TA, Tereshko V, Joachimiak A, Kossiakoff A. The 1.38 A crystal structure of DmsD protein from Salmonella typhimurium, a proofreading chaperone on the Tat pathway. Proteins 2008; 71:525-33. [PMID: 18175314 DOI: 10.1002/prot.21828] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The DmsD protein is necessary for the biogenesis of dimethyl sulphoxide (DMSO) reductase in many prokaryotes. It performs a critical chaperone function initiated through its binding to the twin-arginine signal peptide of DmsA, the catalytic subunit of DMSO reductase. Upon binding to DmsD, DmsA is translocated to the periplasm via the so-called twin-arginine translocation (Tat) pathway. Here we report the 1.38 A crystal structure of the protein DmsD from Salmonella typhimurium and compare it with a close functional homolog, TorD. DmsD has an all-alpha fold structure with a notable helical extension located at its N-terminus with two solvent exposed hydrophobic residues. A major difference between DmsD and TorD is that TorD structure is a domain-swapped dimer, while DmsD exists as a monomer. Nevertheless, these two proteins have a number of common features suggesting they function by using similar mechanisms. A possible signal peptide-binding site is proposed based on structural similarities. Computational analysis was used to identify a potential GTP binding pocket on similar surfaces of DmsD and TorD structures.
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Affiliation(s)
- Yang Qiu
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, USA
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15
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Gerdts CJ, Tereshko V, Yadav MK, Dementieva I, Collart F, Joachimiak A, Stevens RC, Kuhn P, Kossiakoff A, Ismagilov RF. Time-controlled microfluidic seeding in nL-volume droplets to separate nucleation and growth stages of protein crystallization. Angew Chem Int Ed Engl 2007; 45:8156-60. [PMID: 17099920 PMCID: PMC1766323 DOI: 10.1002/anie.200602946] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Cory J. Gerdts
- Department of Chemistry and Institute for Biophysical Dynamics
University of Chicago 5735 S. Ellis Avenue Chicago, IL 60615 (USA)
| | - Valentina Tereshko
- Department of Biochemistry & Molecular Biology University of
Chicago, Chicago, IL (USA)
| | - Maneesh K. Yadav
- Department of Molecular Biology, The Scripps Research Institute La
Jolla, CA (USA)
| | - Irina Dementieva
- Department of Pediatrics, Institute for Molecular Pediatric Sciences
Pritzker School of Medicine, University of Chicago Chicago, IL (USA)
| | - Frank Collart
- Midwest Center for Structural Genomics Argonne National Laboratory,
Argonne, IL (USA)
| | - Andrzej Joachimiak
- Midwest Center for Structural Genomics Argonne National Laboratory,
Argonne, IL (USA)
| | - Raymond C. Stevens
- Department of Molecular Biology, The Scripps Research Institute La
Jolla, CA (USA)
| | - Peter Kuhn
- Department of Cellular Biology, The Scripps Research Institute La
Jolla, CA (USA)
| | - Anthony Kossiakoff
- Department of Biochemistry & Molecular Biology University of
Chicago, Chicago, IL (USA)
| | - Rustem F. Ismagilov
- Department of Cellular Biology, The Scripps Research Institute La
Jolla, CA (USA)
- [*] Fax:
(+1)773-702-0805, E-mail: ,
Homepage: http://ismagilovlab.uchicago.edu/
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Gerdts CJ, Tereshko V, Yadav MK, Dementieva I, Collart F, Joachimiak A, Stevens RC, Kuhn P, Kossiakoff A, Ismagilov RF. Time-Controlled Microfluidic Seeding in nL-Volume Droplets To Separate Nucleation and Growth Stages of Protein Crystallization. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200602946] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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17
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Qiu Y, Tereshko V, Kim Y, Zhang R, Collart F, Yousef M, Kossiakoff A, Joachimiak A. The crystal structure of Aq_328 from the hyperthermophilic bacteria Aquifex aeolicus shows an ancestral histone fold. Proteins 2006; 62:8-16. [PMID: 16287087 PMCID: PMC2792020 DOI: 10.1002/prot.20590] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [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] [Indexed: 01/07/2023]
Abstract
The structure of Aq_328, an uncharacterized protein from hyperthermophilic bacteria Aquifex aeolicus, has been determined to 1.9 A by using multi-wavelength anomalous diffraction (MAD) phasing. Although the amino acid sequence analysis shows that Aq_328 has no significant similarity to proteins with a known structure and function, the structure comparison by using the Dali server reveals that it: (1) assumes a histone-like fold, and (2) is similar to an ancestral nuclear histone protein (PDB code 1F1E) with z-score 8.1 and RMSD 3.6 A over 124 residues. A sedimentation equilibrium experiment indicates that Aq_328 is a monomer in solution, with an average sedimentation coefficient of 2.4 and an apparent molecular weight of about 20 kDa. The overall architecture of Aq_328 consists of two noncanonical histone domains in tandem repeat within a single chain, and is similar to eukaryotic heterodimer (H2A/H2B and H3/H4) and an archaeal histone heterodimer (HMfA/HMfB). The sequence comparisons between the two histone domains of Aq_328 and six eukaryotic/archaeal histones demonstrate that most of the conserved residues that underlie the Aq_328 architecture are used to build and stabilize the two cross-shaped antiparallel histone domains. The high percentage of salt bridges in the structure could be a factor in the protein's thermostability. The structural similarities to other histone-like proteins, molecular properties, and potential function of Aq_328 are discussed in this paper.
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Affiliation(s)
- Yang Qiu
- The University of Chicago, Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois
| | - Valentina Tereshko
- The University of Chicago, Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois
| | - Youngchang Kim
- Structural Biology Center and Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, Illinois
| | - Rongguang Zhang
- Structural Biology Center and Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, Illinois
| | - Frank Collart
- Structural Biology Center and Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, Illinois
| | - Mohammed Yousef
- The University of Chicago, Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois
| | - Anthony Kossiakoff
- The University of Chicago, Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois
| | - Andrzej Joachimiak
- The University of Chicago, Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois
- Structural Biology Center and Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, Illinois
- Correspondence to: Andrzej Joachimiak, Structural Biology Center and Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, 9700 South Cass Avenue, Building 202, Argonne, Illinois 60439. and Anthony Kossia-koff, The University of Chicago, Department of Biochemistry and Molecular Biology, University of Chicago, 920 E. 58 St., Chicago, IL 60637.
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18
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Yi S, Bernat B, Pál G, Kossiakoff A, Li WH. Functional promiscuity of squirrel monkey growth hormone receptor toward both primate and nonprimate growth hormones. Mol Biol Evol 2002; 19:1083-92. [PMID: 12082127 DOI: 10.1093/oxfordjournals.molbev.a004166] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Primate growth hormone (GH) has evolved rapidly, having undergone approximately 30% amino acid substitutions from the inferred ancestral eutherian sequence. Nevertheless, human growth hormone (hGH) is physiologically effective when administered to nonprimate mammals. In contrast, its functional counterpart, the human growth hormone receptor (hGHR), has evolved species specificity so that it responds only to Old World primate GHs. It has been proposed that this species specificity of the hGHR is largely caused by the Leu --> Arg change at position 43 after a prior His --> Asp change at position 171 of the GH. Sequence analyses supported this hypothesis and revealed that the transitional phase in the GH:GHR coevolution still persists in New World monkeys. For example, although the GH of the squirrel monkey has the His --> Asp substitution at position 171, residue 43 of its GHR is a Leu, the nonprimate residue. If the squirrel monkey truly represents an intermediate stage of GH:GHR coevolution, its GHR should respond to both hGH and nonprimate GH. Also, if the emergence of species specificity was a result of the selection for a more efficient GH:GHR interaction, then changing residue 43 of the squirrel monkey growth hormone receptor (smGHR) to Arg should increase its binding affinity toward higher primate GH. To test these hypotheses, we performed protein-binding assays between the smGHR and both human and rat GHs, using the surface plasmon resonance methodology. Furthermore, the effects of reciprocal mutations at position 43 of human and squirrel monkey GHRs are measured for their binding affinities toward human and squirrel monkey GHs. The results from the binding kinetic assays clearly demonstrate that the smGHR is in the intermediate state of the evolution of species specificity. Interestingly, the altered residue Arg at position 43 of the smGHR does not lead to an increased binding affinity. The implications of these results on the evolution of the GH:GHR interaction and on functional evolution are discussed.
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Affiliation(s)
- Soojin Yi
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois 60637, USA.
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19
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Schiffer C, Ultsch M, Walsh S, Somers W, de Vos AM, Kossiakoff A. Structure of a phage display-derived variant of human growth hormone complexed to two copies of the extracellular domain of its receptor: evidence for strong structural coupling between receptor binding sites. J Mol Biol 2002; 316:277-89. [PMID: 11851338 DOI: 10.1006/jmbi.2001.5348] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The structure of the ternary complex between the phage display- optimized, high-affinity Site 1 variant of human growth hormone (hGH) and two copies of the extracellular domain (ECD) of the hGH receptor (hGHR) has been determined at 2.6 A resolution. There are widespread and significant structural differences compared to the wild-type ternary hGH hGHR complex. The hGH variant (hGH(v)) contains 15 Site 1 mutations and binds>10(2) tighter to the hGHR ECD (hGH(R1)) at Site 1. It is biologically active and specific to hGHR. The hGH(v) Site 1 interface is somewhat smaller and 20% more hydrophobic compared to the wild-type (wt) counterpart. Of the ten hormone-receptor H-bonds in the site, only one is the same as in the wt complex. Additionally, several regions of hGH(v) structure move up to 9A in forming the interface. The contacts between the C-terminal domains of two receptor ECDs (hGH(R1)- hGH(R2)) are conserved; however, the large changes in Site 1 appear to cause global changes in the domains of hGH(R1) that affect the hGH(v)-hGH(R2) interface indirectly. This coupling is manifested by large changes in the conformation of groups participating in the Site 2 interaction and results in a structure for the site that is reorganized extensively. The hGH(v)- hGH(R2) interface contains seven H-bonds, only one of which is found in the wt complex. Several groups on hGH(v) and hGH(R2) undergo conformational changes of up to 8 A. Asp116 of hGH(v) plays a central role in the reorganization of Site 2 by forming two new H-bonds to the side-chains of Trp104(R2) and Trp169(R2), which are the key binding determinants of the receptor. The fact that a different binding solution is possible for Site 2, where there were no mutations or binding selection pressures, indicates that the structural elements found in these molecules possess an inherent functional plasticity that enables them to bind to a wide variety of binding surfaces.
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Affiliation(s)
- Celia Schiffer
- Department of Protein Engineering, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
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Abstract
BACKGROUND Intermolecular backbone H-bonding (N-H.O=C) is a common occurrence at the interface of protein-protein complexes. For instance, the amide NH groups of most residues in the binding loop of eglin c, a potent serine proteinase inhibitor from the leech Hirudo medicinalis, are H-bonded to the carbonyl groups of residues in the target enzyme molecules such as chymotrypsin, elastase and subtilisins. We sought to understand the energetic significance of these highly conserved backbone-backbone H-bonds in the enzyme-inhibitor complexes. RESULTS We synthesized an array of backbone-engineered ester analogs of eglin c using native chemical ligation to yield five inhibitor proteins each containing a single backbone ester bond from P3 to P2' (i.e. -CONH-to -COO-). The structure at the ligation site (P6-P5) is essentially unaltered as shown by a high-resolution analysis of the subtilisin-BPN'-eglin c complex. The free-energy changes (DeltaDeltaGNH-->O) associated with the binding of ester analogs at P3, P1 and P2' with bovine alpha-chymotrypsin, subtilisin Carlsberg and porcine pancreatic elastase range from 0-4.5 kcal/mol. Most markedly, the NH-->O substitution at P2 not only stabilizes the inhibitor but also enhances binding to the enzymes by as much as 500-fold. CONCLUSIONS Backbone H-bond contributions are context dependent in the enzyme-eglin c complexes. The interplay of rigidity and adaptability of the binding loop of eglin c seems to play a prominent role in defining the binding action.
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Affiliation(s)
- W Lu
- Gryphon Sciences, 250 East Grand Avenue, Suite 90, South San Francisco, CA 94080, USA.
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21
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Abrahmsén L, Tom J, Burnier J, Butcher KA, Kossiakoff A, Wells JA. Engineering subtilisin and its substrates for efficient ligation of peptide bonds in aqueous solution. Biochemistry 1991; 30:4151-9. [PMID: 2021606 DOI: 10.1021/bi00231a007] [Citation(s) in RCA: 171] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Protein engineering techniques were used to construct a derivative of the serine protease subtilisin that ligates peptides efficiently in water. The subtilisin double mutant in which the catalytic Ser221 was converted to Cys (S221C) and Pro225 converted to Ala (P225A) has 10-fold higher peptide ligase activity and at least 100-fold lower amidase activity than the singly mutated thiolsubtilisin (S221C) that was previously shown to have some peptide ligase activity [Nakatsuka, T., Sasaki, T., & Kaiser, E.T. (1987) J. Am. Chem. Soc. 109, 3808-3810]. A 1.5-A X-ray crystal structure of an oxidized derivative of the double mutant (S221C/P225A) supports the protein design strategy in showing that the P225A mutation partly relieves the steric crowding expected from the S221C substitution, thus accounting for its improved catalytic efficiency. Stable and synthetically reasonable alkyl ester peptide substrates were prepared that rapidly acylate the S221C/P225A enzyme, and aminolysis of the resulting thioacyl-enzyme intermediate by various peptides is strongly preferred over hydrolysis. The efficiency of aminolysis is relatively insensitive to the sequence of the first two residues in the acyl acceptor peptide whose alpha-amino group attacks the thioacyl-enzyme. To obtain greater flexibility in the choice of coupling sites, a set of three additional peptide ligases were engineered by introducing mutations into the parent ligase (S221C/P225A) that were previously shown to change the specificity of subtilisin for the residue nearest the acyl bond (the P1 residue). The specificity properties of the parent ligase and derivatives of it paralleled those of wild type and corresponding specificity variants.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L Abrahmsén
- Department of Protein Engineering, Genentech, Inc., South San Francisco, California 94080
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22
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Bott R, Ultsch M, Kossiakoff A, Graycar T, Katz B, Power S. The three-dimensional structure of Bacillus amyloliquefaciens subtilisin at 1.8 A and an analysis of the structural consequences of peroxide inactivation. J Biol Chem 1988; 263:7895-906. [PMID: 3286644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The three-dimensional structure of the subtilisin from Bacillus amyloliquefaciens (BAS) has been refined to 1.8 A using the amino acid sequence deduced from the DNA coding sequence. The structure is essentially the same as the previously reported structures of subtilisin BPN' (Wright, C.S., Alden, R.A., and Kraut, J. (1969) Nature 221, 235-242) and Novo (Drenth, J., Hol, W. G. J., Jansonius, J. N., and Koekoek, R. (1972) Eur. J. Biochem. 26, 177-181) determined in different crystal forms, at 2.5 and 2.8 A resolution, respectively. The largest differences in the three crystallographic models are seen in regions where the amino acid sequence used in the fit to the electron density maps of BPN' and Novo differs from the gene sequence of BAS (Wells, J. A., Ferrari, E., Henner, D. J., Estell, D. A., and Chen, E. Y. (1983) Nucleic Acids Res. 11, 7911-7925). The refined BAS model shows new features of cation binding, hydrogen bonding, and internal solvent structure. The refined BAS model has served as a basis for the analysis of stereochemical factors involved in the peroxide inactivation of the enzyme. Methionine 222, which is adjacent to the catalytic Ser221, is quantitatively oxidized to the sulfoxide by hydrogen peroxide as had been previously shown for the related Bacillus licheniformis enzyme (Stauffer, C. E., and Etson, D. (1969) J. Biol. Chem. 244, 5333-5338). In addition to this site of modification, we observe partial to full oxidation of two of the four remaining methionines. The oxidation of the methionines does not correlate well with their solvent accessibility calculated from the x-ray structure coordinates; in addition, only one of the two possible stereoisomers of methionine sulfoxide is formed. We also detect hydrogen peroxide-induced modification of the hydroxyl groups of two tyrosines. Modeling suggests that most of the observed effect of oxidation on the enzyme's catalytic efficiency can be attributed to unfavorable interactions at the oxyanion binding site between the sulfoxide group at 222 and the carbonyl oxygen of the scissile peptide bond of the bound substrate.
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Affiliation(s)
- R Bott
- Department of Biomolecular Chemistry, Genentech, Inc., South San Francisco, California 94080
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23
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Bott R, Ultsch M, Kossiakoff A. The structural consequences of site-directed mutations. Acta Crystallogr A 1987. [DOI: 10.1107/s0108767387085155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Katz BA, Kossiakoff A. The crystallographically determined structures of atypical strained disulfides engineered into subtilisin. J Biol Chem 1986; 261:15480-5. [PMID: 3096989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The geometries of two disulfide bridges genetically engineered into subtilisin have been characterized by x-ray crystallography to determine the structural and energetic constraints involved in introducing disulfide bonds into proteins. Both disulfide bridges (Cys-24-Cys-87 and Cys-22-Cys-87) exhibit atypical sets of dihedral angles compared to those for other reported disulfide structures in proteins. The geometric trends for naturally occurring disulfides in protein crystal structures are examined. Comparison of the disulfide-containing mutant protein structures with the wild-type structure shows that, in both cases, disulfide incorporation is accommodated by relatively minor changes in local main-chain conformation. The Cys-22-Cys-87 disulfide has two high energy dihedral angles (X2 = 121 degrees, X2' = 143 degrees). Both disulfides produce short non-bonded contacts with the main-chain.
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