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Kinateder T, Mayer C, Nazet J, Sterner R. Improving enzyme functional annotation by integrating in vitro and in silico approaches: The example of histidinol phosphate phosphatases. Protein Sci 2024; 33:e4899. [PMID: 38284491 PMCID: PMC10804674 DOI: 10.1002/pro.4899] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 12/13/2023] [Accepted: 01/01/2024] [Indexed: 01/30/2024]
Abstract
Advances in sequencing technologies have led to a rapid growth of public protein sequence databases, whereby the fraction of proteins with experimentally verified function continuously decreases. This problem is currently addressed by automated functional annotations with computational tools, which however lack the accuracy of experimental approaches and are susceptible to error propagation. Here, we present an approach that combines the efficiency of functional annotation by in silico methods with the rigor of enzyme characterization in vitro. First, a thorough experimental analysis of a representative enzyme of a group of homologues is performed which includes a focused alanine scan of the active site to determine a fingerprint of function-determining residues. In a second step, this fingerprint is used in combination with a sequence similarity network to identify putative isofunctional enzymes among the homologues. Using this approach in a proof-of-principle study, homologues of the histidinol phosphate phosphatase (HolPase) from Pseudomonas aeruginosa, many of which were annotated as phosphoserine phosphatases, were predicted to be HolPases. This functional annotation of the homologues was verified by in vitro testing of several representatives and an analysis of the occurrence of annotated HolPases in the corresponding phylogenetic groups. Moreover, the application of the same approach to the homologues of the HolPase from the archaeon Nitrosopumilus maritimus, which is not related to the HolPase from P. aeruginosa and was newly discovered in the course of this work, led to the annotation of the putative HolPase from various archaeal species.
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Affiliation(s)
- Thomas Kinateder
- Institute of Biophysics and Physical Biochemistry & Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
| | - Carina Mayer
- Institute of Biophysics and Physical Biochemistry & Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
| | - Julian Nazet
- Institute of Biophysics and Physical Biochemistry & Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
| | - Reinhard Sterner
- Institute of Biophysics and Physical Biochemistry & Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
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2
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Daley SR, Gallanosa PM, Sparling R. Kinetic characterization of annotated glycolytic enzymes present in cellulose-fermenting Clostridium thermocellum suggests different metabolic roles. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:112. [PMID: 37438781 DOI: 10.1186/s13068-023-02362-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 06/27/2023] [Indexed: 07/14/2023]
Abstract
BACKGROUND The efficient production of sustainable biofuels is important for the reduction of greenhouse gas emissions. Clostridium thermocellum ATCC 27405 is a candidate for ethanol production from lignocellulosic biomass using consolidated bioprocessing. Fermentation of cellulosic biomass goes through an atypical glycolytic pathway in this thermophilic bacterium, with various glycolytic enzymes capable of utilizing different phosphate donors, including GTP and inorganic pyrophosphate (PPi), in addition to or in place of the usual ATP. C. thermocellum contains three annotated phosphofructokinases (PFK) genes, the expression of which have all been detected through proteomics and transcriptomics. Pfp (Cthe_0347) was previously characterized as pyrophosphate dependent with fructose-6-phosphate (F6P) as its substrate. RESULTS We now demonstrate that this enzyme can also phosphorylate sedoheptulose-7-phosphate (an intermediate in the pentose phosphate pathway), with the Vmax and Km of F6P being approximately 15 folds higher and 43 folds lower, respectively, in comparison to sedoheptulose-7-phosphate. Purified PfkA shows preference for GTP as the phosphate donor as opposed to ATP with a 12.5-fold difference in Km values while phosphorylating F6P. Allosteric regulation is a factor at play in PfkA activity, with F6P exhibiting positive cooperativity, and an apparent requirement for ammonium ions to attain maximal activity. Phosphoenolpyruvate and PPi were the only inhibitors for PfkA determined from the study, which corroborates what is known about enzymes from this subfamily. The activation or inhibition by these ligands lends support to the argument that glycolysis is regulated by metabolites such as PPi and NH4+ in the organism. PfkB, showed no activity with F6P, but had significant activity with fructose, while utilizing either ATP or GTP, making it a fructokinase. Rounding out the upper glycolysis pathway, the identity of the fructose-1,6-bisphosphate aldolase in the genome was verified and reported to have substantial activity with fructose-1,6-bisphosphate, in the presence of the divalent ion, Zn2+. CONCLUSION These findings along with previous proteomic data suggest that Pfp, plays a role in both glycolysis and the pentose phosphate pathway, while PfkA and PfkB may phosphorylate sugars in glycolysis but is responsible for sugar metabolism elsewhere under conditions outside of growth on sufficient cellobiose.
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Affiliation(s)
- Steve R Daley
- Department of Microbiology, University of Manitoba, 213 Buller Building, Winnipeg, MB, R3T 2N2, Canada
| | - Patricia Mae Gallanosa
- Department of Microbiology, University of Manitoba, 213 Buller Building, Winnipeg, MB, R3T 2N2, Canada
| | - Richard Sparling
- Department of Microbiology, University of Manitoba, 213 Buller Building, Winnipeg, MB, R3T 2N2, Canada.
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3
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Kinateder T, Drexler L, Straub K, Merkl R, Sterner R. Experimental and computational analysis of the ancestry of an evolutionary young enzyme from histidine biosynthesis. Protein Sci 2023; 32:e4536. [PMID: 36502290 PMCID: PMC9798254 DOI: 10.1002/pro.4536] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 12/01/2022] [Accepted: 12/03/2022] [Indexed: 12/14/2022]
Abstract
The conservation of fold and chemistry of the enzymes associated with histidine biosynthesis suggests that this pathway evolved prior to the diversification of Bacteria, Archaea, and Eukaryotes. The only exception is the histidinol phosphate phosphatase (HolPase). So far, non-homologous HolPases that possess distinct folds and belong to three different protein superfamilies have been identified in various phylogenetic clades. However, their evolution has remained unknown to date. Here, we analyzed the evolutionary history of the HolPase from γ-Proteobacteria (HisB-N). It has been argued that HisB-N and its closest homologue d-glycero-d-manno-heptose-1,7-bisphosphate 7-phosphatase (GmhB) have emerged from the same promiscuous ancestral phosphatase. GmhB variants catalyze the hydrolysis of the anomeric d-glycero-d-manno-heptose-1,7-bisphosphate (αHBP or βHBP) with a strong preference for one anomer (αGmhB or βGmhB). We found that HisB-N from Escherichia coli shows promiscuous activity for βHBP but not αHBP, while βGmhB from Crassaminicella sp. shows promiscuous activity for HolP. Accordingly, a combined phylogenetic tree of αGmhBs, βGmhBs, and HisB-N sequences revealed that HisB-Ns form a compact subcluster derived from βGmhBs. Ancestral sequence reconstruction and in vitro analysis revealed a promiscuous HolPase activity in the resurrected enzymes prior to functional divergence of the successors. The following increase in catalytic efficiency of the HolP turnover is reflected in the shape and electrostatics of the active site predicted by AlphaFold. An analysis of the phylogenetic tree led to a revised evolutionary model that proposes the horizontal gene transfer of a promiscuous βGmhB from δ- to γ-Proteobacteria where it evolved to the modern HisB-N.
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Affiliation(s)
- Thomas Kinateder
- Institute of Biophysics and Physical Biochemistry and Regensburg Center for Biochemistry, University of RegensburgRegensburgGermany
| | - Lukas Drexler
- Institute of Biophysics and Physical Biochemistry and Regensburg Center for Biochemistry, University of RegensburgRegensburgGermany
| | - Kristina Straub
- Institute of Biophysics and Physical Biochemistry and Regensburg Center for Biochemistry, University of RegensburgRegensburgGermany
| | - Rainer Merkl
- Institute of Biophysics and Physical Biochemistry and Regensburg Center for Biochemistry, University of RegensburgRegensburgGermany
| | - Reinhard Sterner
- Institute of Biophysics and Physical Biochemistry and Regensburg Center for Biochemistry, University of RegensburgRegensburgGermany
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4
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Discovery and Biotechnological Exploitation of Glycoside-Phosphorylases. Int J Mol Sci 2022; 23:ijms23063043. [PMID: 35328479 PMCID: PMC8950772 DOI: 10.3390/ijms23063043] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/01/2022] [Accepted: 03/03/2022] [Indexed: 02/04/2023] Open
Abstract
Among carbohydrate active enzymes, glycoside phosphorylases (GPs) are valuable catalysts for white biotechnologies, due to their exquisite capacity to efficiently re-modulate oligo- and poly-saccharides, without the need for costly activated sugars as substrates. The reversibility of the phosphorolysis reaction, indeed, makes them attractive tools for glycodiversification. However, discovery of new GP functions is hindered by the difficulty in identifying them in sequence databases, and, rather, relies on extensive and tedious biochemical characterization studies. Nevertheless, recent advances in automated tools have led to major improvements in GP mining, activity predictions, and functional screening. Implementation of GPs into innovative in vitro and in cellulo bioproduction strategies has also made substantial advances. Herein, we propose to discuss the latest developments in the strategies employed to efficiently discover GPs and make the best use of their exceptional catalytic properties for glycoside bioproduction.
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5
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Kropp C, Bruckmann A, Babinger P. Controlling Enzymatic Activity by Modulating the Oligomerization State via Chemical Rescue and Optical Control. Chembiochem 2021; 23:e202100490. [PMID: 34633135 PMCID: PMC9298306 DOI: 10.1002/cbic.202100490] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 10/08/2021] [Indexed: 12/22/2022]
Abstract
Selective switching of enzymatic activity has been a longstanding goal in synthetic biology. Drastic changes in activity upon mutational manipulation of the oligomerization state of enzymes have frequently been reported in the literature, but scarcely exploited for switching. Using geranylgeranylglyceryl phosphate synthase as a model, we demonstrate that catalytic activity can be efficiently controlled by exogenous modulation of the association state. We introduced a lysine‐to‐cysteine mutation, leading to the breakdown of the active hexamer into dimers with impaired catalytic efficiency. Addition of bromoethylamine chemically rescued the enzyme by restoring hexamerization and activity. As an alternative method, we incorporated the photosensitive unnatural amino acid o‐nitrobenzyl‐O‐tyrosine (ONBY) into the hexamerization interface. This again led to inactive dimers, but the hexameric state and activity could be recovered by UV‐light induced cleavage of ONBY. For both approaches, we obtained switching factors greater than 350‐fold, which compares favorably with previously reported activity changes that were caused by site‐directed mutagenesis.
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Affiliation(s)
- Cosimo Kropp
- Institute of Biophysics and Physical Biochemistry, Regensburg Center for Biochemistry, University of Regensburg, 93040, Regensburg, Germany
| | - Astrid Bruckmann
- Institute of Biochemistry, Genetics and Microbiology, Regensburg Center for Biochemistry, University of Regensburg, 93040, Regensburg, Germany
| | - Patrick Babinger
- Institute of Biophysics and Physical Biochemistry, Regensburg Center for Biochemistry, University of Regensburg, 93040, Regensburg, Germany
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6
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ASFV DNA polymerase extends recessed DNAs with catalytic efficiencies outperforming those exerted on gapped DNA substrates. Biochem Biophys Res Commun 2020; 534:526-532. [PMID: 33223051 DOI: 10.1016/j.bbrc.2020.11.049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Accepted: 11/12/2020] [Indexed: 01/17/2023]
Abstract
The DNA polymerase from african swine fever virus (ASFV Pol X), lacking both 8 kDa and thumb domains, is the smallest enzyme featuring competence in DNA extension. Here we show that ASFV Pol X features poor filling activity of DNA gaps consisting of 15 bases, and exerts a more efficient action at the expense of DNA substrates containing a recessed end of equal length. We also show that shortening the recessed end of DNA substrates decreases the rate of DNA elongation catalysed by ASFV Pol X. Finally, by means of stopped-flow experiments we were able to determine that DNA binding is a step responsible for restraining the efficiency of ASFV Pol X catalytic action.
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7
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Hoffmann KM, Goncuian ES, Karimi KL, Amendola CR, Mojab Y, Wood KM, Prussia GA, Nix J, Yamamoto M, Lathan K, Orion IW. Cofactor Complexes of DesD, a Model Enzyme in the Virulence-related NIS Synthetase Family. Biochemistry 2020; 59:3427-3437. [PMID: 32885650 DOI: 10.1021/acs.biochem.9b00899] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The understudied nonribosomal-peptide-synthetase-independent siderophore (NIS) synthetase family has been increasingly associated with virulence in bacterial species due to its key role in the synthesis of hydroxamate and carboxylate "stealth" siderophores. We have identified a model family member, DesD, from Streptomyces coelicolor, to structurally characterize using a combination of a wild-type and a Arg306Gln variant in apo, cofactor product AMP-bound, and cofactor reactant ATP-bound complexes. The kinetics in the family has been limited by solubility and reporter assays, so we have developed a label-free kinetics assay utilizing a single-injection isothermal-titration-calorimetry-based method. We report second-order rate constants that are 50 times higher than the previous estimations for DesD. Our Arg306Gln DesD variant was also tested under identical buffer and substrate conditions, and its undetectable activity was confirmed. These are the first reported structures for DesD, and they describe the critical cofactor coordination. This is also the first label-free assay to unambiguously determine the kinetics for an NIS synthetase.
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Affiliation(s)
- Katherine M Hoffmann
- Department of Chemistry, California Lutheran University, 60 West Olsen Road #3700, Thousand Oaks, California 91360, United States
| | - Eliana S Goncuian
- Department of Chemistry, California Lutheran University, 60 West Olsen Road #3700, Thousand Oaks, California 91360, United States
| | - Kimya L Karimi
- Department of Chemistry, California Lutheran University, 60 West Olsen Road #3700, Thousand Oaks, California 91360, United States
| | - Caroline R Amendola
- Department of Chemistry and Biochemistry, Gonzaga University, 502 East Boone Avenue, Spokane, Washington 99258, United States
| | - Yasi Mojab
- Department of Chemistry, California Lutheran University, 60 West Olsen Road #3700, Thousand Oaks, California 91360, United States
| | - Kaitlin M Wood
- Department of Chemistry and Biochemistry, Gonzaga University, 502 East Boone Avenue, Spokane, Washington 99258, United States
| | - Gregory A Prussia
- Department of Chemistry and Biochemistry, Gonzaga University, 502 East Boone Avenue, Spokane, Washington 99258, United States
| | - Jay Nix
- Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
| | - Margaret Yamamoto
- Department of Chemistry and Biochemistry, Gonzaga University, 502 East Boone Avenue, Spokane, Washington 99258, United States
| | - Kiera Lathan
- Department of Chemistry, California Lutheran University, 60 West Olsen Road #3700, Thousand Oaks, California 91360, United States
| | - Iris W Orion
- Department of Chemistry and Biochemistry, Gonzaga University, 502 East Boone Avenue, Spokane, Washington 99258, United States
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8
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Engineering of Bifunctional Enzymes with Uricase and Peroxidase Activities for Simple and Rapid Quantification of Uric Acid in Biological Samples. Catalysts 2020. [DOI: 10.3390/catal10040428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Serum uric acid (SUA) is an important biomarker for prognosis and management of gout and other diseases. The development of a low-cost, simple, rapid and reliable assay for SUA detection is of great importance. In the present study, to save the cost of enzyme production and to shorten the reaction time for uric acid quantification, bifunctional proteins with uricase and peroxidase activities were engineered. In-frame fusion of Candida utilis uricase (CUOX) and Vitreoscilla hemoglobin (VHb) resulted in two versions of the bifunctional protein, CUOX-VHb (CV) and VHb-CUOX (VC). To our knowledge, this is the first report to describe the production of proteins with uricase and peroxidase activities. Based on the measurement of the initial rates of the coupled reaction (between uricase and peroxidase), CV was proven to be the most efficient enzyme followed by VC and native enzymes (CUOX+VHb), respectively. CV was further applied for the development of an assay for colorimetric detection of SUA, which was based on VHb-catalyzed oxidation of Amplex Red in the presence of hydrogen peroxide (H2O2). Under the optimized conditions, the assay exhibited a linear relationship between the absorbance and UA concentration over the range of 2.5 to 50 μM, with a detection limit of 1 μM. In addition, the assay can be performed at a single pH (8.0) so adjustment of the pH for peroxidase activity was not required. This advantage helped to further reduce costs and time. The developed assay was also successfully applied to detect UA in pooled human serum with the recoveries over 94.8%. These results suggest that the proposed assay holds great potential for clinical application.
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9
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Rice K, Batul K, Whiteside J, Kelso J, Papinski M, Schmidt E, Pratasouskaya A, Wang D, Sullivan R, Bartlett C, Weadge JT, Van der Kamp MW, Moreno-Hagelsieb G, Suits MD, Horsman GP. The predominance of nucleotidyl activation in bacterial phosphonate biosynthesis. Nat Commun 2019; 10:3698. [PMID: 31420548 PMCID: PMC6697681 DOI: 10.1038/s41467-019-11627-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 07/25/2019] [Indexed: 12/22/2022] Open
Abstract
Phosphonates are rare and unusually bioactive natural products. However, most bacterial phosphonate biosynthetic capacity is dedicated to tailoring cell surfaces with molecules like 2-aminoethylphosphonate (AEP). Although phosphoenolpyruvate mutase (Ppm)-catalyzed installation of C-P bonds is known, subsequent phosphonyl tailoring (Pnt) pathway steps remain enigmatic. Here we identify nucleotidyltransferases in over two-thirds of phosphonate biosynthetic gene clusters, including direct fusions to ~60% of Ppm enzymes. We characterize two putative phosphonyl tailoring cytidylyltransferases (PntCs) that prefer AEP over phosphocholine (P-Cho) – a similar substrate used by the related enzyme LicC, which is a virulence factor in Streptococcus pneumoniae. PntC structural analyses reveal steric discrimination against phosphocholine. These findings highlight nucleotidyl activation as a predominant chemical logic in phosphonate biosynthesis and set the stage for probing diverse phosphonyl tailoring pathways. Phosphonate modifications can be present on microbial cell surfaces. Here the authors perform bioinformatics analyses and observe a widespread occurrence of nucleotidyltransferase-encoding genes in bacterial phosphonate biosynthesis and functionally characterize two of the identified phosphonate specific cytidylyltransferases (PntCs) and determine the crystal structure of T. denticola PntC.
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Affiliation(s)
- Kyle Rice
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Kissa Batul
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Jacqueline Whiteside
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Jayne Kelso
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Monica Papinski
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada.,Department of Biology, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Edward Schmidt
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Alena Pratasouskaya
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Dacheng Wang
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Rebecca Sullivan
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Christopher Bartlett
- Department of Biology, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Joel T Weadge
- Department of Biology, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | | | | | - Michael D Suits
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Geoff P Horsman
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada.
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10
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Tee KL, Xu JH, Wong TS. Protein engineering for bioreduction of carboxylic acids. J Biotechnol 2019; 303:53-64. [PMID: 31325477 DOI: 10.1016/j.jbiotec.2019.07.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 07/01/2019] [Accepted: 07/01/2019] [Indexed: 02/07/2023]
Abstract
Carboxylic acids (CAs) are widespread in Nature. A prominent example is fatty acids, a major constituent of lipids. CAs are potentially economical precursors for bio-based products such as bio-aldehydes and bio-alcohols. However, carboxylate reduction is a challenging chemical transformation due to the thermodynamic stability of carboxylate. Carboxylic acid reductases (CARs), found in bacteria and fungi, offer a good solution to this challenge. These enzymes catalyse the NADPH- and ATP-dependent reduction of aliphatic and aromatic CAs. This review summarised all the protein engineering work that has been done on these versatile biocatalysts to date. The intricate catalytic mechanism and structure of CARs prompted us to first examine their domain architecture to facilitate the subsequent discussion of various protein engineering strategies. This then led to a survey of assays to detect aldehyde formation and to monitor aldenylation activity. Strategies for NADPH and ATP regeneration were also incorporated, as they are deemed vital to developing preparative-scale biocatalytic process and high-throughput screening systems. The objectives of the review are to consolidate CAR engineering research, stimulate interest, discussion or debate, and advance the field of bioreduction.
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Affiliation(s)
- Kang Lan Tee
- Department of Chemical & Biological Engineering and Advanced Biomanufacturing Centre, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, United Kingdom
| | - Jian-He Xu
- Laboratory of Biocatalysis and Bioprocessing, State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
| | - Tuck Seng Wong
- Department of Chemical & Biological Engineering and Advanced Biomanufacturing Centre, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, United Kingdom.
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11
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Kovermann M, Stefan A, Castaldo A, Caramia S, Hochkoeppler A. Structural and catalytic insights into HoLaMa, a derivative of Klenow DNA polymerase lacking the proofreading domain. PLoS One 2019; 14:e0215411. [PMID: 30970012 PMCID: PMC6457538 DOI: 10.1371/journal.pone.0215411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 04/01/2019] [Indexed: 11/18/2022] Open
Abstract
We report here on the stability and catalytic properties of the HoLaMa DNA polymerase, a Klenow sub-fragment lacking the 3’-5’ exonuclease domain. HoLaMa was overexpressed in Escherichia coli, and the enzyme was purified by means of standard chromatographic techniques. High-resolution NMR experiments revealed that HoLaMa is properly folded at pH 8.0 and 20°C. In addition, urea induced a cooperative folding to unfolding transition of HoLaMa, possessing an overall thermodynamic stability and a transition midpoint featuring ΔG and CM equal to (15.7 ± 1.9) kJ/mol and (3.5 ± 0.6) M, respectively. When the catalytic performances of HoLaMa were compared to those featured by the Klenow enzyme, we did observe a 10-fold lower catalytic efficiency by the HoLaMa enzyme. Surprisingly, HoLaMa and Klenow DNA polymerases possess markedly different sensitivities in competitive inhibition assays performed to test the effect of single dNTPs.
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Affiliation(s)
- Michael Kovermann
- Department of Chemistry, University of Konstanz, Universitätstraße, Konstanz, Germany
| | - Alessandra Stefan
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
- CSGI, University of Firenze, Sesto Fiorentino (Firenze), Italy
| | - Anna Castaldo
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Sara Caramia
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Alejandro Hochkoeppler
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
- CSGI, University of Firenze, Sesto Fiorentino (Firenze), Italy
- * E-mail:
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12
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Linde M, Heyn K, Merkl R, Sterner R, Babinger P. Hexamerization of Geranylgeranylglyceryl Phosphate Synthase Ensures Structural Integrity and Catalytic Activity at High Temperatures. Biochemistry 2018; 57:2335-2348. [DOI: 10.1021/acs.biochem.7b01284] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Mona Linde
- Institute of Biophysics and Physical Biochemistry, University of Regensburg, 93040 Regensburg, Germany
| | - Kristina Heyn
- Institute of Biophysics and Physical Biochemistry, University of Regensburg, 93040 Regensburg, Germany
| | - Rainer Merkl
- Institute of Biophysics and Physical Biochemistry, University of Regensburg, 93040 Regensburg, Germany
| | - Reinhard Sterner
- Institute of Biophysics and Physical Biochemistry, University of Regensburg, 93040 Regensburg, Germany
| | - Patrick Babinger
- Institute of Biophysics and Physical Biochemistry, University of Regensburg, 93040 Regensburg, Germany
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13
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Grube CD, Roy H. A continuous assay for monitoring the synthetic and proofreading activities of multiple aminoacyl-tRNA synthetases for high-throughput drug discovery. RNA Biol 2017; 15:659-666. [PMID: 29168435 PMCID: PMC6103669 DOI: 10.1080/15476286.2017.1397262] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Aminoacyl-tRNA synthetases (aaRSs) catalyze the aminoacylation of tRNAs to produce the aminoacyl-tRNAs (aa-tRNAs) required by ribosomes for translation of the genetic message into proteins. To ensure the accuracy of tRNA aminoacylation, and consequently the fidelity of protein synthesis, some aaRSs exhibit a proofreading (editing) site, distinct from the aa-tRNA synthetic site. The aaRS editing site hydrolyzes misacylated products formed when a non-cognate amino acid is used during tRNA charging. Because aaRSs play a central role in protein biosynthesis and cellular life, these proteins represent longstanding targets for therapeutic drug development to combat infectious diseases. Most existing aaRS inhibitors target the synthetic site, and it is only recently that drugs targeting the proofreading site have been considered. In the present study, we developed a robust assay for the high-throughput screening of libraries of inhibitors targeting both the synthetic and the proofreading sites of up to four aaRSs simultaneously. Thus, this assay allows for screening of eight distinct enzyme active sites in a single experiment. aaRSs from several prominent human pathogens (i.e., Mycobacterium tuberculosis, Plasmodium falciparum, and Escherichia coli) were used for development of this assay.
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Affiliation(s)
- Christopher D Grube
- a Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida , United States of America
| | - Hervé Roy
- a Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida , United States of America
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14
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The thumb domain is not essential for the catalytic action of HoLaMa DNA polymerase. Protein J 2017; 36:453-460. [DOI: 10.1007/s10930-017-9740-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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15
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The DnaE polymerase from Deinococcus radiodurans features RecA-dependent DNA polymerase activity. Biosci Rep 2016; 36:BSR20160364. [PMID: 27789781 PMCID: PMC5137535 DOI: 10.1042/bsr20160364] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/25/2016] [Accepted: 10/27/2016] [Indexed: 12/25/2022] Open
Abstract
We report in the present study on the catalytic properties of Deinococcus radiodurans DnaE polymerase, whose DNA elongation efficiency was compared with the homologous Escherichia coli polymerase. Contrary to the latter, the deinococcal enzyme was found to be strictly dependent on RecA recombinase. We report in the present study on the catalytic properties of the Deinococcus radiodurans DNA polymerase III α subunit (αDr). The αDr enzyme was overexpressed in Escherichia coli, both in soluble form and as inclusion bodies. When purified from soluble protein extracts, αDr was found to be tightly associated with E. coli RNA polymerase, from which αDr could not be dissociated. On the contrary, when refolded from inclusion bodies, αDr was devoid of E. coli RNA polymerase and was purified to homogeneity. When assayed with different DNA substrates, αDr featured slower DNA extension rates when compared with the corresponding enzyme from E. coli (E. coli DNA Pol III, αEc), unless under high ionic strength conditions or in the presence of manganese. Further assays were performed using a ssDNA and a dsDNA, whose recombination yields a DNA substrate. Surprisingly, αDr was found to be incapable of recombination-dependent DNA polymerase activity, whereas αEc was competent in this action. However, in the presence of the RecA recombinase, αDr was able to efficiently extend the DNA substrate produced by recombination. Upon comparing the rates of RecA-dependent and RecA-independent DNA polymerase activities, we detected a significant activation of αDr by the recombinase. Conversely, the activity of αEc was found maximal under non-recombination conditions. Overall, our observations indicate a sharp contrast between the catalytic actions of αDr and αEc, with αDr more performing under recombination conditions, and αEc preferring DNA substrates whose extension does not require recombination events.
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16
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Lapenta F, Montón Silva A, Brandimarti R, Lanzi M, Gratani FL, Vellosillo Gonzalez P, Perticarari S, Hochkoeppler A. Escherichia coli DnaE Polymerase Couples Pyrophosphatase Activity to DNA Replication. PLoS One 2016; 11:e0152915. [PMID: 27050298 PMCID: PMC4822814 DOI: 10.1371/journal.pone.0152915] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 03/21/2016] [Indexed: 11/19/2022] Open
Abstract
DNA Polymerases generate pyrophosphate every time they catalyze a step of DNA elongation. This elongation reaction is generally believed as thermodynamically favoured by the hydrolysis of pyrophosphate, catalyzed by inorganic pyrophosphatases. However, the specific action of inorganic pyrophosphatases coupled to DNA replication in vivo was never demonstrated. Here we show that the Polymerase-Histidinol-Phosphatase (PHP) domain of Escherichia coli DNA Polymerase III α subunit features pyrophosphatase activity. We also show that this activity is inhibited by fluoride, as commonly observed for inorganic pyrophosphatases, and we identified 3 amino acids of the PHP active site. Remarkably, E. coli cells expressing variants of these catalytic residues of α subunit feature aberrant phenotypes, poor viability, and are subject to high mutation frequencies. Our findings indicate that DNA Polymerases can couple DNA elongation and pyrophosphate hydrolysis, providing a mechanism for the control of DNA extension rate, and suggest a promising target for novel antibiotics.
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Affiliation(s)
- Fabio Lapenta
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | - Alejandro Montón Silva
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | - Renato Brandimarti
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | - Massimiliano Lanzi
- Department of Industrial Chemistry, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | - Fabio Lino Gratani
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | | | - Sofia Perticarari
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | - Alejandro Hochkoeppler
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
- CSGI, University of Firenze, Via della Lastruccia 3, 50019, Sesto Fiorentino, FI, Italy
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17
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Singh D, Schaaper RM, Hochkoeppler A. A continuous spectrophotometric enzyme-coupled assay for deoxynucleoside triphosphate triphosphohydrolases. Anal Biochem 2015; 496:43-9. [PMID: 26723493 DOI: 10.1016/j.ab.2015.11.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 11/19/2015] [Accepted: 11/24/2015] [Indexed: 02/03/2023]
Abstract
We describe a continuous, spectrophotometric, enzyme-coupled assay useful to monitor reactions catalyzed by nucleoside triphosphohydrolases. In particular, using Escherichia coli deoxynucleoside triphosphohydrolase (Dgt), which hydrolyzes dGTP to deoxyguanosine and tripolyphosphate (PPPi) as the enzyme to be tested, we devised a procedure relying on purine nucleoside phosphorylase (PNPase) and xanthine oxidase (XOD) as the auxiliary enzymes. The deoxyguanosine released by Dgt can indeed be conveniently subjected to phosphorolysis by PNPase, yielding deoxyribose-1-phosphate and guanine, which in turn can be oxidized to 8-oxoguanine by XOD. By this means, it was possible to continuously detect Dgt activity at 297 nm, at which wavelength the difference between the molar extinction coefficients of 8-oxoguanine (8000 M(-1) cm(-1)) and guanine (1090 M(-1) cm(-1)) is maximal. The initial velocities of Dgt-catalyzed reactions were then determined in parallel with the enzyme-coupled assay and with a discontinuous high-performance liquid chromatography (HPLC) method able to selectively detect deoxyguanosine. Under appropriate conditions of excess auxiliary enzymes, the activities determined with our continuous enzyme-coupled assay were quantitatively comparable to those observed with the HPLC method. Moreover, the enzyme-coupled assay proved to be more sensitive than the chromatographic procedure, permitting reliable detection of Dgt activity at low dGTP substrate concentrations.
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Affiliation(s)
- Deepa Singh
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Roel M Schaaper
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Alejandro Hochkoeppler
- Department of Pharmacy and Biotechnology, University of Bologna, 40136 Bologna, Italy; CSGI, University of Firenze, 50019 Sesto Fiorentino, FI, Italy.
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18
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Forget SM, Jee A, Smithen DA, Jagdhane R, Anjum S, Beaton SA, Palmer DRJ, Syvitski RT, Jakeman DL. Kinetic evaluation of glucose 1-phosphate analogues with a thymidylyltransferase using a continuous coupled enzyme assay. Org Biomol Chem 2015; 13:866-75. [PMID: 25408103 DOI: 10.1039/c4ob02057j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cps2L, a thymidylytransferase, is the first enzyme in Streptococcus pneumoniae L-rhamnose biosynthesis and an antibacterial target. We herein report the evaluation of six sugar phosphate analogues selected to further probe Cps2L substrate tolerance. A modified continuous spectrophotometric assay was employed for facile detection of pyrophosphate (PPi) released from nucleotidylyltransfase-catalysed condensation of sugar 1-phosphates and nucleoside triphosphates to produce sugar nucleotides. Additionally, experiments using waterLOGSY NMR spectroscopy were investigated as a complimentary method to evaluate binding affinity to Cps2L.
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Affiliation(s)
- S M Forget
- Department of Chemistry, Dalhousie University, 6274 Coburg Rd, PO Box 15, 000, Halifax, Nova Scotia B3H 4R2, Canada.
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19
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Montón Silva A, Lapenta F, Stefan A, Dal Piaz F, Ceccarelli A, Perrone A, Hochkoeppler A. Simultaneous ternary extension of DNA catalyzed by a trimeric replicase assembled in vivo. Biochem Biophys Res Commun 2015; 462:14-20. [PMID: 25918025 DOI: 10.1016/j.bbrc.2015.04.067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 04/12/2015] [Indexed: 10/23/2022]
Abstract
According to current models, dimeric DNA Polymerases coordinate the replication of DNA leading and lagging strands. However, it was recently shown that trimeric DNA Polymerases, assembled in vitro, replicate the lagging strand more efficiently than dimeric replicases. Here we show that the τ, α, ε, and θ subunits of Escherichia coli DNA Polymerase III can be assembled in vivo, yielding the trimeric τ3α3ε3θ3 complex. Further, we propose a molecular model of this complex, whose catalytic action was investigated using model DNA substrates. Our observations indicate that trimeric DNA replicases reduce the gap between leading and lagging strand synthesis.
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Affiliation(s)
- Alejandro Montón Silva
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Fabio Lapenta
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Alessandra Stefan
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy; CSGI, University of Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, FI, Italy
| | - Fabrizio Dal Piaz
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, SA, Italy
| | - Alessandro Ceccarelli
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Alessandro Perrone
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Alejandro Hochkoeppler
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy; CSGI, University of Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, FI, Italy.
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20
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Martina CE, Lapenta F, Montón Silva A, Hochkoeppler A. HoLaMa: A Klenow sub-fragment lacking the 3'-5' exonuclease domain. Arch Biochem Biophys 2015; 575:46-53. [PMID: 25906742 DOI: 10.1016/j.abb.2015.04.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 04/14/2015] [Indexed: 11/30/2022]
Abstract
The design, construction, overexpression, and purification of a Klenow sub-fragment lacking the 3'-5' exonuclease domain is presented here. In particular, a synthetic gene coding for the residues 515-928 of Escherichia coli DNA polymerase I was constructed. To improve the solubility and stability of the corresponding protein, the synthetic gene was designed to contain 11 site-specific substitutions. The gene was inserted into the pBADHis expression vector, generating 2 identical Klenow sub-fragments, bearing or not a hexahistidine tag. Both these Klenow sub-fragments, denominated HoLaMa and HoLaMaHis, were purified, and their catalytic properties were compared to those of Klenow enzyme. When DNA polymerase activity was assayed under processive conditions, the Klenow enzyme performed much better than HoLaMa and HoLaMaHis. However, when DNA polymerase activity was assayed under distributive conditions, the initial velocity of the reaction catalyzed by HoLaMa was comparable to that observed in the presence of Klenow enzyme. In particular, under distributive conditions HoLaMa was found to strongly prefer dsDNAs bearing a short template overhang, to the length of which the Klenow enzyme was relatively insensitive. Overall, our observations indicate that the exonuclease domain of the Klenow enzyme, besides its proofreading activity, does significantly contribute to the catalytic efficiency of DNA elongation.
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Affiliation(s)
- Cristina Elisa Martina
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Fabio Lapenta
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Alejandro Montón Silva
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Alejandro Hochkoeppler
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy; CSGI, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, FI, Italy.
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21
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Stefan A, Ceccarelli A, Conte E, Montón Silva A, Hochkoeppler A. The multifaceted benefits of protein co-expression in Escherichia coli. J Vis Exp 2015. [PMID: 25742393 DOI: 10.3791/52431] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
We report here that the expression of protein complexes in vivo in Escherichia coli can be more convenient than traditional reconstitution experiments in vitro. In particular, we show that the poor solubility of Escherichia coli DNA polymerase III ε subunit (featuring 3'-5' exonuclease activity) is highly improved when the same protein is co-expressed with the α and θ subunits (featuring DNA polymerase activity and stabilizing ε, respectively). We also show that protein co-expression in E. coli can be used to efficiently test the competence of subunits from different bacterial species to associate in a functional protein complex. We indeed show that the α subunit of Deinococcus radiodurans DNA polymerase III can be co-expressed in vivo with the ε subunit of E. coli. In addition, we report on the use of protein co-expression to modulate mutation frequency in E. coli. By expressing the wild-type ε subunit under the control of the araBAD promoter (arabinose-inducible), and co-expressing the mutagenic D12A variant of the same protein, under the control of the lac promoter (inducible by isopropyl-thio-β-D-galactopyranoside, IPTG), we were able to alter the E. coli mutation frequency using appropriate concentrations of the inducers arabinose and IPTG. Finally, we discuss recent advances and future challenges of protein co-expression in E. coli.
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Affiliation(s)
- Alessandra Stefan
- Department of Pharmacy and Biotechnology, University of Bologna; CSGI, Department of Chemistry, University of Firenze
| | | | - Emanuele Conte
- Department of Pharmacy and Biotechnology, University of Bologna
| | | | - Alejandro Hochkoeppler
- Department of Pharmacy and Biotechnology, University of Bologna; CSGI, Department of Chemistry, University of Firenze;
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22
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Montgomery JL, Wittwer CT. Influence of PCR reagents on DNA polymerase extension rates measured on real-time PCR instruments. Clin Chem 2013; 60:334-40. [PMID: 24081987 DOI: 10.1373/clinchem.2013.212829] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Radioactive DNA polymerase activity methods are cumbersome and do not provide initial extension rates. A simple extension rate assay would enable study of basic assumptions about PCR and define the limits of rapid PCR. METHODS A continuous assay that monitors DNA polymerase extension using noncovalent DNA dyes on common real-time PCR instruments was developed. Extension rates were measured in nucleotides per second per molecule of polymerase. To initiate the reaction, a nucleotide analog was heat activated at 95 °C for 5 min, the temperature decreased to 75 °C, and fluorescence monitored until substrate exhaustion in 30-90 min. RESULTS The assay was linear with time for over 40% of the reaction and for polymerase concentrations over a 100-fold range (1-100 pmol/L). Extension rates decreased continuously with increasing monovalent cation concentrations (lithium, sodium, potassium, cesium, and ammonium). Melting-temperature depressors had variable effects. DMSO increased rates up to 33%, whereas glycerol had little effect. Betaine, formamide, and 1,2-propanediol decreased rates with increasing concentrations. Four common noncovalent DNA dyes inhibited polymerase extension. Heat-activated nucleotide analogs were 92% activated after 5 min, and hot start DNA polymerases were 73%-90% activated after 20 min. CONCLUSIONS Simple DNA extension rate assays can be performed on real-time PCR instruments. Activity is decreased by monovalent cations, DNA dyes, and most melting temperature depressors. Rational inclusion of PCR components on the basis of their effects on polymerase extension is likely to be useful in PCR, particularly rapid-cycle or fast PCR.
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Affiliation(s)
- Jesse L Montgomery
- Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, UT
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23
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Montgomery JL, Rejali N, Wittwer CT. Stopped-flow DNA polymerase assay by continuous monitoring of dNTP incorporation by fluorescence. Anal Biochem 2013; 441:133-9. [PMID: 23872003 DOI: 10.1016/j.ab.2013.07.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 07/03/2013] [Accepted: 07/06/2013] [Indexed: 11/29/2022]
Abstract
DNA polymerase activity was measured by a stopped-flow assay that monitors polymerase extension using an intercalating dye. Double-stranded DNA formation during extension of a hairpin substrate was monitored at 75°C for 2 min. Rates were determined in nucleotides per second per molecule of polymerase (nt/s) and were linear with time and polymerase concentration from 1 to 50 nM. The concentrations of 15 available polymerases were quantified and their extension rates determined in 50 mM Tris, pH 8.3, 0.5 mg/ml BSA, 2 mM MgCl₂, and 200 μM each dNTP as well as their commercially recommended buffers. Native Taq polymerases had similar extension rates of 10-45 nt/s. Three alternative polymerases showed faster speeds, including KOD (76 nt/s), Klentaq I (101 nt/s), and KAPA2G (155 nt/s). Fusion polymerases including Herculase II and Phusion were relatively slow (3-13 nt/s). The pH optimum for Klentaq extension was between 8.5 and 8.7 with no effect of Tris concentration. Activity was directly correlated to the MgCl2 concentration and inversely correlated to the KCl concentration. This continuous assay is relevant to PCR and provides accurate measurement of polymerase activity using a defined template without the need of radiolabeled substrates.
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Affiliation(s)
- Jesse L Montgomery
- Department of Pathology, University of Utah, Salt Lake City, UT 84132, USA
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