1
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Wu T, Yu JC, Suresh A, Gale-Day ZJ, Alteen MG, Woo AS, Millbern Z, Johnson OT, Carroll EC, Partch CL, Fourches D, Vinueza NR, Vocadlo DJ, Gestwicki JE. Protein-adaptive differential scanning fluorimetry using conformationally responsive dyes. Nat Biotechnol 2024:10.1038/s41587-024-02158-7. [PMID: 38744946 DOI: 10.1038/s41587-024-02158-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 01/31/2024] [Indexed: 05/16/2024]
Abstract
Differential scanning fluorimetry (DSF) is a technique that reports protein thermal stability via the selective recognition of unfolded states by fluorogenic dyes. However, DSF applications remain limited by protein incompatibilities with existing DSF dyes. Here we overcome this obstacle with the development of a protein-adaptive DSF platform (paDSF) that combines a dye library 'Aurora' with a streamlined procedure to identify protein-dye pairs on demand. paDSF was successfully applied to 94% (66 of 70) of proteins, tripling the previous compatibility and delivering assays for 66 functionally and biochemically diverse proteins, including 10 from severe acute respiratory syndrome coronavirus 2. We find that paDSF can be used to monitor biological processes that were previously inaccessible, demonstrated for the interdomain allostery of O-GlcNAc transferase. The chemical diversity and varied selectivities of Aurora dyes suggest that paDSF functionality may be readily extended. paDSF is a generalizable tool to interrogate protein stability, dynamics and ligand binding.
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Affiliation(s)
- Taiasean Wu
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
- Institute for Neurodegenerative Diseases, University of California, San Francisco, CA, USA
| | - Joshua C Yu
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Arundhati Suresh
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Zachary J Gale-Day
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Matthew G Alteen
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Amanda S Woo
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Zoe Millbern
- Department of Textile Engineering, North Carolina State University, Raleigh, NC, USA
| | - Oleta T Johnson
- Institute for Neurodegenerative Diseases, University of California, San Francisco, CA, USA
| | - Emma C Carroll
- Institute for Neurodegenerative Diseases, University of California, San Francisco, CA, USA
| | - Carrie L Partch
- Department of Chemistry, University of California, Santa Cruz, CA, USA
| | - Denis Fourches
- Department of Textile Engineering, North Carolina State University, Raleigh, NC, USA
| | - Nelson R Vinueza
- Department of Textile Engineering, North Carolina State University, Raleigh, NC, USA
| | - David J Vocadlo
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Jason E Gestwicki
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA.
- Institute for Neurodegenerative Diseases, University of California, San Francisco, CA, USA.
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2
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Majumder P, Ahmed S, Ahuja P, Athreya A, Ranjan R, Penmatsa A. Cryo-EM structure of antibacterial efflux transporter QacA from Staphylococcus aureus reveals a novel extracellular loop with allosteric role. EMBO J 2023; 42:e113418. [PMID: 37458117 PMCID: PMC10425836 DOI: 10.15252/embj.2023113418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Revised: 06/21/2023] [Accepted: 06/26/2023] [Indexed: 07/18/2023] Open
Abstract
Efflux of antibacterial compounds is a major mechanism for developing antimicrobial resistance. In the Gram-positive pathogen Staphylococcus aureus, QacA, a 14 transmembrane helix containing major facilitator superfamily antiporter, mediates proton-coupled efflux of mono and divalent cationic antibacterial compounds. In this study, we report the cryo-EM structure of QacA, with a single mutation D411N that improves homogeneity and retains efflux activity against divalent cationic compounds like dequalinium and chlorhexidine. The structure of substrate-free QacA, complexed to two single-domain camelid antibodies, was elucidated to a resolution of 3.6 Å. The structure displays an outward-open conformation with an extracellular helical hairpin loop (EL7) between transmembrane helices 13 and 14, which is conserved in a subset of DHA2 transporters. Removal of the EL7 hairpin loop or disrupting the interface formed between EL7 and EL1 compromises efflux activity. Chimeric constructs of QacA with a helical hairpin and EL1 grafted from other DHA2 members, LfrA and SmvA, restore activity in the EL7 deleted QacA revealing the allosteric and vital role of EL7 hairpin in antibacterial efflux in QacA and related members.
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Affiliation(s)
- Puja Majumder
- Molecular Biophysics UnitIndian Institute of ScienceBangaloreIndia
- Present address:
Memorial‐Sloan Kettering Cancer CenterNew YorkNYUSA
| | - Shahbaz Ahmed
- Molecular Biophysics UnitIndian Institute of ScienceBangaloreIndia
- Present address:
St. Jude Children's Research HospitalMemphisTNUSA
| | - Pragya Ahuja
- Molecular Biophysics UnitIndian Institute of ScienceBangaloreIndia
| | - Arunabh Athreya
- Molecular Biophysics UnitIndian Institute of ScienceBangaloreIndia
| | - Rakesh Ranjan
- ICAR‐National Research Centre on CamelJorbeerBikanerIndia
| | - Aravind Penmatsa
- Molecular Biophysics UnitIndian Institute of ScienceBangaloreIndia
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3
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Kanjo K, Chattopadhyay G, Malladi SK, Singh R, Jayatheertha S, Varadarajan R. Biophysical Correlates of Enhanced Immunogenicity of a Stabilized Variant of the Receptor Binding Domain of SARS-CoV-2. J Phys Chem B 2023; 127:1704-1714. [PMID: 36790910 PMCID: PMC9942533 DOI: 10.1021/acs.jpcb.2c07262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The receptor binding domain (RBD) of SARS-CoV-2 is the primary target of neutralizing antibodies. We have previously reported the design and characterization of a mammalian cell expressed RBD derivative, mRBD1-3.2, that has higher thermal stability and greatly enhanced immunogenicity relative to the wild type mRBD. The protein is highly thermotolerant and immunogenic and is being explored for use in room temperature stable Covid-19 vaccine formulations. In the current study, we have investigated the folding pathway of both WT and stabilized RBD. It was found that chemical denaturation of RBD proceeds through a stable equilibrium intermediate. Thermal and chemical denaturation is reversible, as assayed by binding to the receptor ACE2. Unusually, in its native state, RBD binds to the hydrophobic probe ANS, and enhanced ANS binding is observed for the equilibrium intermediate state. Further characterization of the folding of mRBD1-3.2, both in solution and after reconstitution of lyophilized protein stored for a month at 37 °C, revealed a higher stability represented by higher Cm, faster refolding, slower unfolding, and enhanced resistance to proteolytic cleavage relative to WT. In contrast to WT RBD, the mutant showed decreased interaction with the hydrophobic moiety linoleic acid. Collectively, these data suggest that the enhanced immunogenicity results from reduced conformational fluctuations that likely enhance in vivo half-life as well as reduce the exposure of irrelevant non-neutralizing epitopes to the immune system.
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Affiliation(s)
- Kawkab Kanjo
- Molecular Biophysics Unit (MBU), Indian Institute of Science, Bengaluru 560012, India
| | | | - Sameer Kumar Malladi
- Molecular Biophysics Unit (MBU), Indian Institute of Science, Bengaluru 560012, India
| | - Randhir Singh
- Mynvax Private Limited, Fourth Floor, Brigade MLR Center, 50, Vanivilas Rd, Gandhi Bazaar, Basavanagudi, Bangalore, Karnataka 560004, India
| | - Sowrabha Jayatheertha
- Mynvax Private Limited, Fourth Floor, Brigade MLR Center, 50, Vanivilas Rd, Gandhi Bazaar, Basavanagudi, Bangalore, Karnataka 560004, India
| | - Raghavan Varadarajan
- Molecular Biophysics Unit (MBU), Indian Institute of Science, Bengaluru 560012, India.,Mynvax Private Limited, Fourth Floor, Brigade MLR Center, 50, Vanivilas Rd, Gandhi Bazaar, Basavanagudi, Bangalore, Karnataka 560004, India
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4
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Chandra S, Manjunath K, Asok A, Varadarajan R. Mutational scan inferred binding energetics and structure in intrinsically disordered protein CcdA. Protein Sci 2023; 32:e4580. [PMID: 36714997 PMCID: PMC9951195 DOI: 10.1002/pro.4580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 01/02/2023] [Accepted: 01/25/2023] [Indexed: 01/31/2023]
Abstract
Unlike globular proteins, mutational effects on the function of Intrinsically Disordered Proteins (IDPs) are not well-studied. Deep Mutational Scanning of a yeast surface displayed mutant library yields insights into sequence-function relationships in the CcdA IDP. The approach enables facile prediction of interface residues and local structural signatures of the bound conformation. In contrast to previous titration-based approaches which use a number of ligand concentrations, we show that use of a single rationally chosen ligand concentration can provide quantitative estimates of relative binding constants for large numbers of protein variants. This is because the extended interface of IDP ensures that energetic effects of point mutations are spread over a much smaller range than for globular proteins. Our data also provides insights into the much-debated role of helicity and disorder in partner binding of IDPs. Based on this exhaustive mutational sensitivity dataset, a rudimentary model was developed in an attempt to predict mutational effects on binding affinity of IDPs that form alpha-helical structures upon binding.
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Affiliation(s)
| | | | - Aparna Asok
- Molecular Biophysics Unit, Indian Institute of ScienceBangaloreIndia
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5
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Chattopadhyay G, Ahmed S, Srilatha NS, Asok A, Varadarajan R. Ter-Seq: A high-throughput method to stabilize transient ternary complexes and measure associated kinetics. Protein Sci 2023; 32:e4514. [PMID: 36382921 PMCID: PMC9793979 DOI: 10.1002/pro.4514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/01/2022] [Accepted: 11/14/2022] [Indexed: 11/17/2022]
Abstract
Regulation of biological processes by proteins often involves the formation of transient, multimeric complexes whose characterization is mechanistically important but challenging. The bacterial toxin CcdB binds and poisons DNA Gyrase. The corresponding antitoxin CcdA extracts CcdB from its complex with Gyrase through the formation of a transient ternary complex, thus rejuvenating Gyrase. We describe a high throughput methodology called Ter-Seq to stabilize probable ternary complexes and measure associated kinetics using the CcdA-CcdB-GyrA14 ternary complex as a model system. The method involves screening a yeast surface display (YSD) saturation mutagenesis library of one partner (CcdB) for mutants that show enhanced ternary complex formation. We also isolated CcdB mutants that were either resistant or sensitive to rejuvenation, and used surface plasmon resonance (SPR) with purified proteins to validate the kinetics measured using the surface display. Positions, where CcdB mutations lead to slower rejuvenation rates, are largely involved in CcdA-binding, though there were several notable exceptions suggesting allostery. Mutations at these positions reduce the affinity towards CcdA, thereby slowing down the rejuvenation process. Mutations at GyrA14-interacting positions significantly enhanced rejuvenation rates, either due to reduced affinity or complete loss of CcdB binding to GyrA14. We examined the effect of different parameters (CcdA affinity, GyrA14 affinity, surface accessibilities, evolutionary conservation) on the rate of rejuvenation. Finally, we further validated the Ter-Seq results by monitoring the kinetics of ternary complex formation for individual CcdB mutants in solution by fluorescence resonance energy transfer (FRET) studies.
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Affiliation(s)
- Gopinath Chattopadhyay
- Molecular Biophysics UnitIndian Institute of ScienceBangaloreIndia
- Institute for Evolutionary Biology and Environmental SciencesUniversity of ZurichZurichSwitzerland
| | - Shahbaz Ahmed
- Molecular Biophysics UnitIndian Institute of ScienceBangaloreIndia
- St. Jude Children's Research HospitalTennesseeUSA
| | | | - Aparna Asok
- Molecular Biophysics UnitIndian Institute of ScienceBangaloreIndia
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6
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Ahmed S, Chattopadhyay G, Manjunath K, Bhasin M, Singh N, Rasool M, Das S, Rana V, Khan N, Mitra D, Asok A, Singh R, Varadarajan R. Combining cysteine scanning with chemical labeling to map protein-protein interactions and infer bound structure in an intrinsically disordered region. Front Mol Biosci 2022; 9:997653. [PMID: 36275627 PMCID: PMC9585320 DOI: 10.3389/fmolb.2022.997653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 09/12/2022] [Indexed: 11/13/2022] Open
Abstract
The Mycobacterium tuberculosis genome harbours nine toxin-antitoxin (TA) systems of the mazEF family. These consist of two proteins, a toxin and an antitoxin, encoded in an operon. While the toxin has a conserved fold, the antitoxins are structurally diverse and the toxin binding region is typically intrinsically disordered before binding. We describe high throughput methodology for accurate mapping of interfacial residues and apply it to three MazEF complexes. The method involves screening one partner protein against a panel of chemically masked single cysteine mutants of its interacting partner, displayed on the surface of yeast cells. Such libraries have much lower diversity than those generated by saturation mutagenesis, simplifying library generation and data analysis. Further, because of the steric bulk of the masking reagent, labeling of virtually all exposed epitope residues should result in loss of binding, and buried residues are inaccessible to the labeling reagent. The binding residues are deciphered by probing the loss of binding to the labeled cognate partner by flow cytometry. Using this methodology, we have identified the interfacial residues for MazEF3, MazEF6 and MazEF9 TA systems of M. tuberculosis. In the case of MazEF9, where a crystal structure was available, there was excellent agreement between our predictions and the crystal structure, superior to those with AlphaFold2. We also report detailed biophysical characterization of the MazEF3 and MazEF9 TA systems and measured the relative affinities between cognate and non-cognate toxin–antitoxin partners in order to probe possible cross-talk between these systems.
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Affiliation(s)
- Shahbaz Ahmed
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | | | | | - Munmun Bhasin
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Neelam Singh
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, Faridabad, India
| | - Mubashir Rasool
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Sayan Das
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, Faridabad, India
| | - Varsha Rana
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Neha Khan
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, Faridabad, India
| | - Debarghya Mitra
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Aparna Asok
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Ramandeep Singh
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, Faridabad, India
| | - Raghavan Varadarajan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
- *Correspondence: Raghavan Varadarajan,
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7
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Candido KL, Eich CR, de Fariña LO, Kadowaki MK, da Conceição Silva JL, Maller A, Simão RDCG. Spike protein of SARS-CoV-2 variants: a brief review and practical implications. Braz J Microbiol 2022; 53:1133-1157. [PMID: 35397075 PMCID: PMC8994061 DOI: 10.1007/s42770-022-00743-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Accepted: 03/21/2022] [Indexed: 12/24/2022] Open
Abstract
The scientific community has been alarmed by the possible immunological evasion, higher infectivity, and severity of disease caused by the newest variants of SARS-CoV-2. The spike protein has an important role in the cellular invasion of viruses and is the target of several vaccines and therapeutic resources, such as monoclonal antibodies. In addition, some of the most relevant mutations in the different variants are on the spike (S) protein gene sequence that leads to structural alterations in the predicted protein, thus causing concern about the protection mediated by vaccines against these new strains. The present review highlights the most recent knowledge about COVID-19 and vaccines, emphasizing the different spike protein structures of SARS-CoV-2 and updating the reader about the emerging viral variants and their classifications, the more common viral mutations described and their distribution in Brazil. It also compiles a table with the most recent knowledge about all of the Omicron spike mutations.
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Affiliation(s)
- Kattlyn Laryssa Candido
- Present Address: Laboratório de Bioquímica Molecular (LaBioqMol), Centro de Ciências Médicas e Farmacêuticas, Unioeste, Cascavel, PR Brazil
| | - Caio Ricardo Eich
- Present Address: Laboratório de Bioquímica Molecular (LaBioqMol), Centro de Ciências Médicas e Farmacêuticas, Unioeste, Cascavel, PR Brazil
| | - Luciana Oliveira de Fariña
- Present Address: Laboratório de Bioquímica Molecular (LaBioqMol), Centro de Ciências Médicas e Farmacêuticas, Unioeste, Cascavel, PR Brazil
| | - Marina Kimiko Kadowaki
- Present Address: Laboratório de Bioquímica Molecular (LaBioqMol), Centro de Ciências Médicas e Farmacêuticas, Unioeste, Cascavel, PR Brazil
| | - José Luis da Conceição Silva
- Present Address: Laboratório de Bioquímica Molecular (LaBioqMol), Centro de Ciências Médicas e Farmacêuticas, Unioeste, Cascavel, PR Brazil
| | - Alexandre Maller
- Present Address: Laboratório de Bioquímica Molecular (LaBioqMol), Centro de Ciências Médicas e Farmacêuticas, Unioeste, Cascavel, PR Brazil
| | - Rita de Cássia Garcia Simão
- Present Address: Laboratório de Bioquímica Molecular (LaBioqMol), Centro de Ciências Médicas e Farmacêuticas, Unioeste, Cascavel, PR Brazil
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8
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Majorina MA, Melnik TN, Glukhov AS, Melnik BS. Some useful ideas for multistate protein design: Effect of amino acid substitutions on the multistate proteins stability and the rate of protein structure formation. Front Mol Biosci 2022; 9:983009. [PMID: 36090043 PMCID: PMC9462454 DOI: 10.3389/fmolb.2022.983009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 07/19/2022] [Indexed: 11/13/2022] Open
Abstract
The design of new protein variants is usually confined to slightly “fixing” an already existing protein, adapting it to certain conditions or to a new substrate. This is relatively easy to do if the fragment of the protein to be affected, such as the active site of the protein, is known. But what if you need to “fix” the stability of a protein or the rate of its native or intermediate state formation? Having studied a large number of protein mutant forms, we have established the effect of various amino acid substitutions on the energy landscape of the protein. As a result, we have revealed a number of patterns to help researchers identify amino acid residues that determine the folding rate and the stability of globular proteins states and design a mutant form of a protein with desired properties.
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Affiliation(s)
- M. A. Majorina
- Institute of Protein Research, Russian Academy of Sciences, Moscow, Russia
| | - T. N. Melnik
- Institute of Protein Research, Russian Academy of Sciences, Moscow, Russia
| | - A. S. Glukhov
- Institute of Protein Research, Russian Academy of Sciences, Moscow, Russia
| | - B. S. Melnik
- Institute of Protein Research, Russian Academy of Sciences, Moscow, Russia
- Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- *Correspondence: B. S. Melnik,
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9
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Chattopadhyay G, Bhowmick J, Manjunath K, Ahmed S, Goyal P, Varadarajan R. Mechanistic insights into global suppressors of protein folding defects. PLoS Genet 2022; 18:e1010334. [PMID: 36037221 PMCID: PMC9491731 DOI: 10.1371/journal.pgen.1010334] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 09/09/2022] [Accepted: 07/11/2022] [Indexed: 01/14/2023] Open
Abstract
Most amino acid substitutions in a protein either lead to partial loss-of-function or are near neutral. Several studies have shown the existence of second-site mutations that can rescue defects caused by diverse loss-of-function mutations. Such global suppressor mutations are key drivers of protein evolution. However, the mechanisms responsible for such suppression remain poorly understood. To address this, we characterized multiple suppressor mutations both in isolation and in combination with inactive mutants. We examined six global suppressors of the bacterial toxin CcdB, the known M182T global suppressor of TEM-1 β-lactamase, the N239Y global suppressor of p53-DBD and three suppressors of the SARS-CoV-2 spike Receptor Binding Domain. When coupled to inactive mutants, they promote increased in-vivo solubilities as well as regain-of-function phenotypes. In the case of CcdB, where novel suppressors were isolated, we determined the crystal structures of three such suppressors to obtain insight into the specific molecular interactions responsible for the observed effects. While most individual suppressors result in small stability enhancements relative to wildtype, which can be combined to yield significant stability increments, thermodynamic stabilisation is neither necessary nor sufficient for suppressor action. Instead, in diverse systems, we observe that individual global suppressors greatly enhance the foldability of buried site mutants, primarily through increase in refolding rate parameters measured in vitro. In the crowded intracellular environment, mutations that slow down folding likely facilitate off-pathway aggregation. We suggest that suppressor mutations that accelerate refolding can counteract this, enhancing the yield of properly folded, functional protein in vivo.
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Affiliation(s)
| | - Jayantika Bhowmick
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore,
India
| | - Kavyashree Manjunath
- Centre for Chemical Biology and Therapeutics, Institute For Stem Cell
Science and Regenerative Medicine, Bangalore, India
| | - Shahbaz Ahmed
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore,
India
| | - Parveen Goyal
- Institute for Stem Cell Science and Regenerative Medicine, Bangalore,
India
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10
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Chattopadhyay G, Bhasin M, Ahmed S, Gosain TP, Ganesan S, Das S, Thakur C, Chandra N, Singh R, Varadarajan R. Functional and Biochemical Characterization of the MazEF6 Toxin-Antitoxin System of Mycobacterium tuberculosis. J Bacteriol 2022; 204:e0005822. [PMID: 35357163 PMCID: PMC9053165 DOI: 10.1128/jb.00058-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Accepted: 03/07/2022] [Indexed: 12/15/2022] Open
Abstract
The Mycobacterium tuberculosis genome harbors nine toxin-antitoxin (TA) systems that are members of the mazEF family, unlike other prokaryotes, which have only one or two. Although the overall tertiary folds of MazF toxins are predicted to be similar, it is unclear how they recognize structurally different RNAs and antitoxins with divergent sequence specificity. Here, we have expressed and purified the individual components and complex of the MazEF6 TA system from M. tuberculosis. Size exclusion chromatography-multiangle light scattering (SEC-MALS) was performed to determine the oligomerization status of the toxin, antitoxin, and the complex in different stoichiometric ratios. The relative stabilities of the proteins were determined by nano-differential scanning fluorimetry (nano-DSF). Microscale thermophoresis (MST) and yeast surface display (YSD) were performed to measure the relative affinities between the cognate toxin-antitoxin partners. The interaction between MazEF6 complexes and cognate promoter DNA was also studied using MST. Analysis of paired-end RNA sequencing data revealed that the overexpression of MazF6 resulted in differential expression of 323 transcripts in M. tuberculosis. Network analysis was performed to identify the nodes from the top-response network. The analysis of mRNA protection ratios resulted in identification of putative MazF6 cleavage site in its native host, M. tuberculosis. IMPORTANCE M. tuberculosis harbors a large number of type II toxin-antitoxin (TA) systems, the exact roles for most of which are unclear. Prior studies have reported that overexpression of several of these type II toxins inhibits bacterial growth and contributes to the formation of drug-tolerant populations in vitro. To obtain insights into M. tuberculosis MazEF6 type II TA system function, we determined stability, oligomeric states, and binding affinities of cognate partners with each other and with their promoter operator DNA. Using RNA-seq data obtained from M. tuberculosis overexpression strains, we have identified putative MazF6 cleavage sites and targets in its native, cellular context.
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Affiliation(s)
| | - Munmun Bhasin
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, India
| | - Shahbaz Ahmed
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, India
| | - Tannu Priya Gosain
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Srivarshini Ganesan
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, Tamil Nadu, India
| | - Sayan Das
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Chandrani Thakur
- Department of Biochemistry, Indian Institute of Science, Bangalore, Karnataka, India
| | - Nagasuma Chandra
- Department of Biochemistry, Indian Institute of Science, Bangalore, Karnataka, India
| | - Ramandeep Singh
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Raghavan Varadarajan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, India
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11
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Ahmed S, Manjunath K, Chattopadhyay G, Varadarajan R. Identification of stabilizing point mutations through mutagenesis of destabilized protein libraries. J Biol Chem 2022; 298:101785. [PMID: 35247389 PMCID: PMC8971944 DOI: 10.1016/j.jbc.2022.101785] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 02/18/2022] [Accepted: 02/26/2022] [Indexed: 01/22/2023] Open
Abstract
Although there have been recent transformative advances in the area of protein structure prediction, prediction of point mutations that improve protein stability remains challenging. It is possible to construct and screen large mutant libraries for improved activity or ligand binding. However, reliable screens for mutants that improve protein stability do not yet exist, especially for proteins that are well folded and relatively stable. Here, we demonstrate that incorporation of a single, specific, destabilizing mutation termed parent inactivating mutation into each member of a single-site saturation mutagenesis library, followed by screening for suppressors, allows for robust and accurate identification of stabilizing mutations. We carried out fluorescence-activated cell sorting of such a yeast surface display, saturation suppressor library of the bacterial toxin CcdB, followed by deep sequencing of sorted populations. We found that multiple stabilizing mutations could be identified after a single round of sorting. In addition, multiple libraries with different parent inactivating mutations could be pooled and simultaneously screened to further enhance the accuracy of identification of stabilizing mutations. Finally, we show that individual stabilizing mutations could be combined to result in a multi-mutant that demonstrated an increase in thermal melting temperature of about 20 °C, and that displayed enhanced tolerance to high temperature exposure. We conclude that as this method is robust and employs small library sizes, it can be readily extended to other display and screening formats to rapidly isolate stabilized protein mutants.
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Affiliation(s)
- Shahbaz Ahmed
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Kavyashree Manjunath
- Centre for Chemical Biology and Therapeutics, Institute of Stem Cell Science and Regenerative Medicine, Bangalore, India
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