1
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Kennedy EN, Foster CA, Barr SA, Bourret RB. General strategies for using amino acid sequence data to guide biochemical investigation of protein function. Biochem Soc Trans 2022; 50:1847-1858. [PMID: 36416676 PMCID: PMC10257402 DOI: 10.1042/bst20220849] [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: 08/18/2022] [Revised: 11/04/2022] [Accepted: 11/09/2022] [Indexed: 11/24/2022]
Abstract
The rapid increase of '-omics' data warrants the reconsideration of experimental strategies to investigate general protein function. Studying individual members of a protein family is likely insufficient to provide a complete mechanistic understanding of family functions, especially for diverse families with thousands of known members. Strategies that exploit large amounts of available amino acid sequence data can inspire and guide biochemical experiments, generating broadly applicable insights into a given family. Here we review several methods that utilize abundant sequence data to focus experimental efforts and identify features truly representative of a protein family or domain. First, coevolutionary relationships between residues within primary sequences can be successfully exploited to identify structurally and/or functionally important positions for experimental investigation. Second, functionally important variable residue positions typically occupy a limited sequence space, a property useful for guiding biochemical characterization of the effects of the most physiologically and evolutionarily relevant amino acids. Third, amino acid sequence variation within domains shared between different protein families can be used to sort a particular domain into multiple subtypes, inspiring further experimental designs. Although generally applicable to any kind of protein domain because they depend solely on amino acid sequences, the second and third approaches are reviewed in detail because they appear to have been used infrequently and offer immediate opportunities for new advances. Finally, we speculate that future technologies capable of analyzing and manipulating conserved and variable aspects of the three-dimensional structures of a protein family could lead to broad insights not attainable by current methods.
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Affiliation(s)
- Emily N. Kennedy
- Department of Microbiology & Immunology, University of North Carolina, Chapel Hill, NC, United States of America
| | - Clay A. Foster
- Department of Pediatrics, Section Hematology/Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Sarah A. Barr
- Department of Microbiology & Immunology, University of North Carolina, Chapel Hill, NC, United States of America
| | - Robert B. Bourret
- Department of Microbiology & Immunology, University of North Carolina, Chapel Hill, NC, United States of America
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2
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Vass LR, Branscum KM, Bourret RB, Foster CA. Generalizable strategy to analyze domains in the context of parent protein architecture: A CheW case study. Proteins 2022; 90:1973-1986. [PMID: 35668544 PMCID: PMC9561059 DOI: 10.1002/prot.26390] [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: 03/02/2022] [Revised: 05/31/2022] [Accepted: 06/02/2022] [Indexed: 11/08/2022]
Abstract
Domains are the three-dimensional building blocks of proteins. An individual domain can occur in a variety of domain architectures that perform unique functions and are subject to different evolutionary selective pressures. We describe an approach to evaluate the variability in amino acid sequences of a single domain across architectural contexts. The ability to distinguish different evolutionary outcomes of one protein domain can help determine whether existing knowledge about a specific domain will apply to an uncharacterized protein, lead to insights and hypotheses about function, and guide experimental priorities. We developed and tested our approach on CheW-like domains (PF01584), which mediate protein/protein interactions and are difficult to compare experimentally. CheW-like domains occur in CheW scaffolding proteins, CheA kinases, and CheV proteins that regulate bacterial chemotaxis. We analyzed 16 domain architectures that included 94% of all CheW-like domains found in nature. We identified six Classes of CheW-like domains with presumed functional differences. CheV and most CheW proteins contained Class 1 domains, whereas some CheW proteins contained Class 6 (~20%) or Class 2 (~1%) domains instead. Most CheA proteins contained Class 3 domains. CheA proteins with multiple Hpt domains contained Class 4 domains. CheA proteins with two CheW-like domains contained one Class 3 and one Class 5. We also created SimpLogo, an innovative method for visualizing amino acid composition across large sets of multiple sequence alignments of arbitrary length. SimpLogo offers substantial advantages over standard sequence logos for comparison and analysis of related protein sequences. The R package for SimpLogo is freely available.
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Affiliation(s)
- Luke R. Vass
- Department of Microbiology & Immunology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Current Address: Department of Pathology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Katie M. Branscum
- Current Address: Department of Pediatrics, Section Hematology/Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Robert B. Bourret
- Department of Microbiology & Immunology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Clay A. Foster
- Department of Microbiology & Immunology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Current Address: Department of Pediatrics, Section Hematology/Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
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3
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Azorhizobium caulinodans chemotaxis is controlled by an unusual phosphorelay network. J Bacteriol 2021; 204:e0052721. [PMID: 34843377 DOI: 10.1128/jb.00527-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Azorhizobium caulinodans is a nitrogen-fixing bacterium that forms root nodules on its host legume, Sesbania rostrata. This agriculturally significant symbiotic relationship is important in lowland rice cultivation, and allows for nitrogen fixation under flood conditions. Chemotaxis plays an important role in bacterial colonization of the rhizosphere. Plant roots release chemical compounds that are sensed by bacteria, triggering chemotaxis along a concentration gradient toward the roots. This gives motile bacteria a significant competitive advantage during root surface colonization. Although plant-associated bacterial genomes often encode multiple chemotaxis systems, A. caulinodans appears to encode only one. The che cluster on the A. caulinodans genome contains cheA, cheW, cheY2, cheB, and cheR. Two other chemotaxis genes, cheY1 and cheZ, are located independently from the che operon. Both CheY1 and CheY2 are involved in chemotaxis, with CheY1 being the predominant signaling protein. A. caulinodans CheA contains an unusual set of C-terminal domains: a CheW-like/Receiver pair (termed W2-Rec), follows the more common single CheW-like domain. W2-Rec impacts both chemotaxis and CheA function. We found a preference for transfer of phosphoryl groups from CheA to CheY2, rather than to W2-Rec or CheY1, which appears to be involved in flagellar motor binding. Furthermore, we observed increased phosphoryl group stabilities on CheY1 compared to CheY2 or W2-Rec. Finally, CheZ enhanced dephosphorylation of CheY2 substantially more than CheY1, but had no effect on the dephosphorylation rate of W2-Rec. This network of phosphotransfer reactions highlights a previously uncharacterized scheme for regulation of chemotactic responses. IMPORTANCE Chemotaxis allows bacteria to move towards nutrients and away from toxins in their environment. Chemotactic movement provides a competitive advantage over non-specific motion. CheY is an essential mediator of the chemotactic response with phosphorylated and unphosphorylated forms of CheY differentially interacting with the flagellar motor to change swimming behavior. Previously established schemes of CheY dephosphorylation include action of a phosphatase and/or transfer of the phosphoryl group to another receiver domain that acts as a sink. Here, we propose A. caulinodans uses a concerted mechanism in which the Hpt domain of CheA, CheY2, and CheZ function together as a dual sink system to rapidly reset chemotactic signaling. To the best of our knowledge, this mechanism is unlike any that have previously been evaluated. Chemotaxis systems that utilize both receiver and Hpt domains as phosphate sinks likely occur in other bacterial species.
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4
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Predicted Functional and Structural Diversity of Receiver Domains in Fungal Two-Component Regulatory Systems. mSphere 2021; 6:e0072221. [PMID: 34612676 PMCID: PMC8510515 DOI: 10.1128/msphere.00722-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Fungal two-component regulatory systems incorporate receiver domains into hybrid histidine kinases (HHKs) and response regulators. We constructed a nonredundant database of 670 fungal receiver domain sequences from 51 species sampled from nine fungal phyla. A much greater proportion (21%) of predicted fungal response regulators did not belong to known groups than previously appreciated. Receiver domains in Rim15 response regulators from Ascomycota and other phyla are very different from one another, as are the duplicate receiver domains in group XII HHKs. Fungal receiver domains from five known types of response regulators and 20 known types of HHKs exhibit distinct patterns of amino acids at conserved and variable positions known to be structurally and functionally important in bacterial receiver domains. We inferred structure/activity relationships from the patterns and propose multiple experimentally testable hypotheses about the mechanisms of signal transduction mediated by fungal receiver domains.
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Foster CA, Silversmith RE, Immormino RM, Vass LR, Kennedy EN, Pazy Y, Collins EJ, Bourret RB. Role of Position K+4 in the Phosphorylation and Dephosphorylation Reaction Kinetics of the CheY Response Regulator. Biochemistry 2021; 60:2130-2151. [PMID: 34167303 DOI: 10.1021/acs.biochem.1c00246] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two-component signaling is a primary method by which microorganisms interact with their environments. A kinase detects stimuli and modulates autophosphorylation activity. The signal propagates by phosphotransfer from the kinase to a response regulator, eliciting a response. Response regulators operate over a range of time scales, corresponding to their related biological processes. Response regulator active site chemistry is highly conserved, but certain variable residues can influence phosphorylation kinetics. An Ala-to-Pro substitution (K+4, residue 113) in the Escherichia coli response regulator CheY triggers a constitutively active phenotype; however, the A113P substitution is too far from the active site to directly affect phosphochemistry. To better understand the activating mechanism(s) of the substitution, we analyzed receiver domain sequences to characterize the evolutionary role of the K+4 position. Although most featured Pro, Leu, Ile, and Val residues, chemotaxis-related proteins exhibited atypical Ala, Gly, Asp, and Glu residues at K+4. Structural and in silico analyses revealed that CheY A113P adopted a partially active configuration. Biochemical data showed that A113P shifted CheY toward a more activated state, enhancing autophosphorylation. By characterizing CheY variants, we determined that this functionality was transmitted through a hydrophobic network bounded by the β5α5 loop and the α1 helix of CheY. This region also interacts with the phosphodonor CheAP1, suggesting that binding generates an activating perturbation similar to the A113P substitution. Atypical residues like Ala at the K+4 position likely serve two purposes. First, restricting autophosphorylation may minimize background noise generated by intracellular phosphodonors such as acetyl phosphate. Second, optimizing interactions with upstream partners may help prime the receiver domain for phosphorylation.
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Affiliation(s)
- Clay A Foster
- Department of Microbiology and Immunology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Ruth E Silversmith
- Department of Microbiology and Immunology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Robert M Immormino
- Department of Microbiology and Immunology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Luke R Vass
- Department of Microbiology and Immunology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Emily N Kennedy
- Department of Microbiology and Immunology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Yael Pazy
- Department of Microbiology and Immunology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Edward J Collins
- Department of Microbiology and Immunology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Robert B Bourret
- Department of Microbiology and Immunology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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6
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The Development of Bacteriophage Resistance in Vibrio alginolyticus Depends on a Complex Metabolic Adaptation Strategy. Viruses 2021; 13:v13040656. [PMID: 33920240 PMCID: PMC8069663 DOI: 10.3390/v13040656] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 04/07/2021] [Accepted: 04/08/2021] [Indexed: 12/23/2022] Open
Abstract
Lytic bacteriophages have been well documented to play a pivotal role in microbial ecology due to their complex interactions with bacterial species, especially in aquatic habitats. Although the use of phages as antimicrobial agents, known as phage therapy, in the aquatic environment has been increasing, recent research has revealed drawbacks due to the development of phage-resistant strains among Gram-negative species. Acquired phage resistance in marine Vibrios has been proven to be a very complicated process utilizing biochemical, metabolic, and molecular adaptation strategies. The results of our multi-omics approach, incorporating transcriptome and metabolome analyses of Vibrio alginolyticus phage-resistant strains, corroborate this prospect. Our results provide insights into phage-tolerant strains diminishing the expression of phage receptors ompF, lamB, and btuB. The same pattern was observed for genes encoding natural nutrient channels, such as rbsA, ptsG, tryP, livH, lysE, and hisp, meaning that the cell needs to readjust its biochemistry to achieve phage resistance. The results showed reprogramming of bacterial metabolism by transcript regulations in key-metabolic pathways, such as the tricarboxylic acid cycle (TCA) and lysine biosynthesis, as well as the content of intracellular metabolites belonging to processes that could also significantly affect the cell physiology. Finally, SNP analysis in resistant strains revealed no evidence of amino acid alterations in the studied putative bacterial phage receptors, but several SNPs were detected in genes involved in transcriptional regulation. This phenomenon appears to be a phage-specific, fine-tuned metabolic engineering, imposed by the different phage genera the bacteria have interacted with, updating the role of lytic phages in microbial marine ecology.
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7
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Abdizadeh H, Jalalypour F, Atilgan AR, Atilgan C. A Coarse-Grained Methodology Identifies Intrinsic Mechanisms That Dissociate Interacting Protein Pairs. Front Mol Biosci 2020; 7:210. [PMID: 33195399 PMCID: PMC7477071 DOI: 10.3389/fmolb.2020.00210] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 08/03/2020] [Indexed: 11/13/2022] Open
Abstract
We address the problem of triggering dissociation events between proteins that have formed a complex. We have collected a set of 25 non-redundant, functionally diverse protein complexes having high-resolution three-dimensional structures in both the unbound and bound forms. We unify elastic network models with perturbation response scanning (PRS) methodology as an efficient approach for predicting residues that have the propensity to trigger dissociation of an interacting protein pair, using the three-dimensional structures of the bound and unbound proteins as input. PRS reveals that while for a group of protein pairs, residues involved in the conformational shifts are confined to regions with large motions, there are others where they originate from parts of the protein unaffected structurally by binding. Strikingly, only a few of the complexes have interface residues responsible for dissociation. We find two main modes of response: In one mode, remote control of dissociation in which disruption of the electrostatic potential distribution along protein surfaces play the major role; in the alternative mode, mechanical control of dissociation by remote residues prevail. In the former, dissociation is triggered by changes in the local environment of the protein, e.g., pH or ionic strength, while in the latter, specific perturbations arriving at the controlling residues, e.g., via binding to a third interacting partner is required for decomplexation. We resolve the observations by relying on an electromechanical coupling model which reduces to the usual elastic network result in the limit of the lack of coupling. We validate the approach by illustrating the biological significance of top residues selected by PRS on select cases where we show that the residues whose perturbation leads to the observed conformational changes correspond to either functionally important or highly conserved residues in the complex.
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Affiliation(s)
- Haleh Abdizadeh
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, Netherlands
| | - Farzaneh Jalalypour
- Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey
| | - Ali Rana Atilgan
- Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey
| | - Canan Atilgan
- Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey
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8
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Wang J, Jain A, McDonald LR, Gambogi C, Lee AL, Dokholyan NV. Mapping allosteric communications within individual proteins. Nat Commun 2020; 11:3862. [PMID: 32737291 PMCID: PMC7395124 DOI: 10.1038/s41467-020-17618-2] [Citation(s) in RCA: 88] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Accepted: 06/30/2020] [Indexed: 02/05/2023] Open
Abstract
Allostery in proteins influences various biological processes such as regulation of gene transcription and activities of enzymes and cell signaling. Computational approaches for analysis of allosteric coupling provide inexpensive opportunities to predict mutations and to design small-molecule agents to control protein function and cellular activity. We develop a computationally efficient network-based method, Ohm, to identify and characterize allosteric communication networks within proteins. Unlike previously developed simulation-based approaches, Ohm relies solely on the structure of the protein of interest. We use Ohm to map allosteric networks in a dataset composed of 20 proteins experimentally identified to be allosterically regulated. Further, the Ohm allostery prediction for the protein CheY correlates well with NMR CHESCA studies. Our webserver, Ohm.dokhlab.org, automatically determines allosteric network architecture and identifies critical coupled residues within this network.
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Affiliation(s)
- Jian Wang
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, 17033-0850, USA
| | - Abha Jain
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7363, USA
| | - Leanna R McDonald
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7363, USA
| | - Craig Gambogi
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7363, USA
| | - Andrew L Lee
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7363, USA
| | - Nikolay V Dokholyan
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, 17033-0850, USA.
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
- Departments of Biochemistry & Molecular Biology, Penn State College of Medicine, Hershey, PA, 17033-0850, USA.
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9
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Modulation of Response Regulator CheY Reaction Kinetics by Two Variable Residues That Affect Conformation. J Bacteriol 2020; 202:JB.00089-20. [PMID: 32424010 DOI: 10.1128/jb.00089-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 05/09/2020] [Indexed: 01/16/2023] Open
Abstract
Microorganisms and plants utilize two-component systems to regulate adaptive responses to changing environmental conditions. Sensor kinases detect stimuli and alter their autophosphorylation activity accordingly. Signal propagation occurs via the transfer of phosphoryl groups from upstream kinases to downstream response regulator proteins. Removal of phosphoryl groups from the response regulator typically resets the system. Members of the same protein family may catalyze phosphorylation and dephosphorylation reactions with different efficiencies, exhibiting rate constants spanning many orders of magnitude to accommodate response time scales from milliseconds to days. We previously found that variable positions one or two residues to the C-terminal side of the conserved Asp phosphorylation site (D+2) or Thr/Ser (T+1/T+2) in response regulators alter reaction kinetics by direct interaction with phosphodonor or phosphoacceptor molecules. Here, we explore the kinetic effects of amino acid substitutions at the two positions immediately C-terminal to the conserved Lys (K+1/K+2) in the model Escherichia coli response regulator CheY. We measured CheY autophosphorylation and autodephosphorylation rate constants for 27 pairs of K+1/K+2 residues that represent 84% of naturally occurring response regulators. Effects on autodephosphorylation were modest, but autophosphorylation rate constants varied by 2 orders of magnitude, suggesting that the K+1/K+2 positions influence reaction kinetics by altering the conformational spectrum sampled by CheY at equilibrium. Additional evidence supporting this indirect mechanism includes the following: the effect on autophosphorylation rate constants is independent of the phosphodonor, the autophosphorylation rate constants and dissociation constants for the phosphoryl group analog BeF3 - are inversely correlated, and the K+1/K+2 positions are distant from the phosphorylation site.IMPORTANCE We have identified five variable positions in response regulators that allow the rate constants of autophosphorylation and autodephosporylation reactions each to be altered over 3 orders of magnitude in CheY. The distributions of variable residue combinations across response regulator subfamilies suggest that distinct mechanisms associated with different variable positions allow reaction rates to be tuned independently during evolution for diverse biological purposes. This knowledge could be used in synthetic-biology applications to adjust the properties (e.g., background noise and response duration) of biosensors and may allow prediction of response regulator reaction kinetics from the primary amino acid sequence.
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10
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Hochstrasser R, Hutter CAJ, Arnold FM, Bärlocher K, Seeger MA, Hilbi H. The structure of the
Legionella
response regulator LqsR reveals amino acids critical for phosphorylation and dimerization. Mol Microbiol 2020; 113:1070-1084. [DOI: 10.1111/mmi.14477] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 01/20/2020] [Accepted: 01/21/2020] [Indexed: 12/16/2022]
Affiliation(s)
- Ramon Hochstrasser
- Institute of Medical Microbiology University of Zürich Zürich Switzerland
| | | | - Fabian M. Arnold
- Institute of Medical Microbiology University of Zürich Zürich Switzerland
| | - Kevin Bärlocher
- Institute of Medical Microbiology University of Zürich Zürich Switzerland
| | - Markus A. Seeger
- Institute of Medical Microbiology University of Zürich Zürich Switzerland
| | - Hubert Hilbi
- Institute of Medical Microbiology University of Zürich Zürich Switzerland
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11
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Abstract
Response regulators function as the output components of two-component systems, which couple the sensing of environmental stimuli to adaptive responses. Response regulators typically contain conserved receiver (REC) domains that function as phosphorylation-regulated switches to control the activities of effector domains that elicit output responses. This modular design is extremely versatile, enabling different regulatory strategies tuned to the needs of individual signaling systems. This review summarizes structural features that underlie response regulator function. An abundance of atomic resolution structures and complementary biochemical data have defined the mechanisms for response regulator enzymatic activities, revealed trends in regulatory strategies utilized by response regulators of different subfamilies, and provided insights into interactions of response regulators with their cognate histidine kinases. Among the hundreds of thousands of response regulators identified, variations abound. This article provides a framework for understanding structural features that enable function of canonical response regulators and a basis for distinguishing noncanonical configurations.
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Affiliation(s)
- Rong Gao
- Center for Advanced Biotechnology and Medicine, Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA; , ,
| | - Sophie Bouillet
- Center for Advanced Biotechnology and Medicine, Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA; , ,
| | - Ann M Stock
- Center for Advanced Biotechnology and Medicine, Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA; , ,
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12
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Bourret RB, Silversmith RE. Measuring the Activities of Two-Component Regulatory System Phosphatases. Methods Enzymol 2018; 607:321-351. [PMID: 30149864 DOI: 10.1016/bs.mie.2018.05.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Two-component regulatory systems (TCSs) are used for signal transduction by organisms from all three phylogenetic domains of the living world. TCSs use transient protein phosphorylation and dephosphorylation reactions to convert stimuli into appropriate responses to changing environmental conditions. Phosphoryl groups flow from ATP to sensor kinases (which detect stimuli) to response regulators (which implement responses) to inorganic phosphate (Pi). The phosphorylation state of response regulators controls their output activity. The rate at which phosphoryl groups are removed from response regulators correlates with the timescale of the corresponding biological function. Dephosphorylation reactions are fastest in chemotaxis TCS and slower in other TCS. Response regulators catalyze their own dephosphorylation, but at least five types of phosphatases are known to enhance dephosphorylation of response regulators. In each case, the phosphatases are believed to stimulate the intrinsic autodephosphorylation reaction. We discuss in depth the properties of TCS (particularly the differences between chemotaxis and nonchemotaxis TCS) relevant to designing in vitro assays for TCS phosphatases. We describe detailed assay methods for chemotaxis TCS phosphatases using loss of 32P, change in intrinsic fluorescence as a result of dephosphorylation, or release of Pi. The phosphatase activities of nonchemotaxis TCS phosphatases are less well characterized. We consider how the properties of nonchemotaxis TCS affect assay design and suggest suitable modifications for phosphatases from nonchemotaxis TCS, with an emphasis on the Pi release method.
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Affiliation(s)
- Robert B Bourret
- Department of Microbiology & Immunology, University of North Carolina, Chapel Hill, NC, United States.
| | - Ruth E Silversmith
- Department of Microbiology & Immunology, University of North Carolina, Chapel Hill, NC, United States
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13
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Silversmith RE, Bourret RB. Fluorescence Measurement of Kinetics of CheY Autophosphorylation with Small Molecule Phosphodonors. Methods Mol Biol 2018; 1729:321-335. [PMID: 29429101 DOI: 10.1007/978-1-4939-7577-8_25] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The Escherichia coli chemotaxis protein CheY is a model receiver domain containing a native tryptophan residue that serves as a fluorescent probe for CheY autophosphorylation with small molecule phosphodonors. Here we describe fluorescence measurement of apparent bimolecular rate constants for reaction of wild type and mutant CheY with phosphodonors acetyl phosphate, phosphoramidate, or monophosphoimidazole. Step-by-step protocols to synthesize phosphoramidate (K+ salt) and monophosphoimidazole (Na+ salt), which are not commercially available, are provided. Key factors to consider in developing autophosphorylation assays for other response regulators are also discussed.
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Affiliation(s)
- Ruth E Silversmith
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC, USA
| | - Robert B Bourret
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC, USA.
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14
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Trajtenberg F, Imelio JA, Machado MR, Larrieux N, Marti MA, Obal G, Mechaly AE, Buschiazzo A. Regulation of signaling directionality revealed by 3D snapshots of a kinase:regulator complex in action. eLife 2016; 5:e21422. [PMID: 27938660 PMCID: PMC5231405 DOI: 10.7554/elife.21422] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Accepted: 12/09/2016] [Indexed: 01/19/2023] Open
Abstract
Two-component systems (TCS) are protein machineries that enable cells to respond to input signals. Histidine kinases (HK) are the sensory component, transferring information toward downstream response regulators (RR). HKs transfer phosphoryl groups to their specific RRs, but also dephosphorylate them, overall ensuring proper signaling. The mechanisms by which HKs discriminate between such disparate directions, are yet unknown. We now disclose crystal structures of the HK:RR complex DesK:DesR from Bacillus subtilis, comprising snapshots of the phosphotransfer and the dephosphorylation reactions. The HK dictates the reactional outcome through conformational rearrangements that include the reactive histidine. The phosphotransfer center is asymmetric, poised for dissociative nucleophilic substitution. The structural bases of HK phosphatase/phosphotransferase control are uncovered, and the unexpected discovery of a dissociative reactional center, sheds light on the evolution of TCS phosphotransfer reversibility. Our findings should be applicable to a broad range of signaling systems and instrumental in synthetic TCS rewiring.
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Affiliation(s)
- Felipe Trajtenberg
- Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Juan A Imelio
- Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Matías R Machado
- Biomolecular Simulations, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Nicole Larrieux
- Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Marcelo A Marti
- Departamento de Química Biológica e IQUIBICEN-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Gonzalo Obal
- Protein Biophysics Unit, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Ariel E Mechaly
- Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Alejandro Buschiazzo
- Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
- Département de Microbiologie, Institut Pasteur, Paris, France
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15
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Immormino RM, Silversmith RE, Bourret RB. A Variable Active Site Residue Influences the Kinetics of Response Regulator Phosphorylation and Dephosphorylation. Biochemistry 2016; 55:5595-5609. [PMID: 27589219 PMCID: PMC5050157 DOI: 10.1021/acs.biochem.6b00645] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Two-component regulatory systems, minimally composed of a sensor kinase and a response regulator protein, are common mediators of signal transduction in microorganisms. All response regulators contain a receiver domain with conserved active site residues that catalyze the signal activating and deactivating phosphorylation and dephosphorylation reactions. We explored the impact of variable active site position T+1 (one residue C-terminal to the conserved Thr/Ser) on reaction kinetics and signaling fidelity, using wild type and mutant Escherichia coli CheY, CheB, and NarL to represent the three major sequence classes observed across response regulators: Ala/Gly, Ser/Thr, and Val/Ile/Met, respectively, at T+1. Biochemical and structural data together suggested that different amino acids at T+1 impacted reaction kinetics by altering access to the active site while not perturbing overall protein structure. A given amino acid at position T+1 had similar effects on autodephosphorylation in each protein background tested, likely by modulating access of the attacking water molecule to the active site. Similarly, rate constants for CheY autophosphorylation with three different small molecule phosphodonors were consistent with the steric constraints on access to the phosphorylation site arising from combination of specific phosphodonors with particular amino acids at T+1. Because other variable active site residues also influence response regulator phosphorylation biochemistry, we began to explore how context (here, the amino acid at T+2) affected the influence of position T+1 on CheY autocatalytic reactions. Finally, position T+1 affected the fidelity and kinetics of phosphotransfer between sensor kinases and response regulators but was not a primary determinant of their interaction.
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Affiliation(s)
| | - Ruth E. Silversmith
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina 27599-7290, United States
| | - Robert B. Bourret
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina 27599-7290, United States
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16
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Experimental Analysis of Functional Variation within Protein Families: Receiver Domain Autodephosphorylation Kinetics. J Bacteriol 2016; 198:2483-93. [PMID: 27381915 DOI: 10.1128/jb.00853-15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2015] [Accepted: 06/28/2016] [Indexed: 01/13/2023] Open
Abstract
UNLABELLED Plants and microorganisms use two-component signal transduction systems (TCSs) to mediate responses to environmental stimuli. TCSs mediate responses through phosphotransfer from a conserved histidine on a sensor kinase to a conserved aspartate on the receiver domain of a response regulator. Typically, signal termination occurs through dephosphorylation of the receiver domain, which can catalyze its own dephosphorylation. Despite strong structural conservation between receiver domains, reported autodephosphorylation rate constants (kdephos) span a millionfold range. Variable receiver domain active-site residues D + 2 and T + 2 (two amino acids C terminal to conserved phosphorylation site and Thr/Ser, respectively) influence kdephos values, but the extent and mechanism of influence are unclear. We used sequence analysis of a large database of naturally occurring receiver domains to design mutant receiver domains for experimental analysis of autodephosphorylation kinetics. When combined with previous analyses, kdephos values were obtained for CheY variants that contained D + 2/T + 2 pairs found in 54% of receiver domain sequences. Tested pairs of amino acids at D + 2/T + 2 generally had similar effects on kdephos in CheY, PhoBN, or Spo0F. Acid or amide residues at D + 2/T + 2 enhanced kdephos CheY variants altered at D + 2/T + 2 exhibited rate constants for autophosphorylation with phosphoramidates and autodephosphorylation that were inversely correlated, suggesting that D + 2/T + 2 residues interact with aspects of the ground or transition states that differ between the two reactions. kdephos of CheY variants altered at D + 2/T + 2 correlated significantly with kdephos of wild-type receiver domains containing the same D + 2/T + 2 pair. Additionally, particular D + 2/T + 2 pairs were enriched in different response regulator subfamilies, suggesting functional significance. IMPORTANCE One protein family, defined by a conserved domain, can include hundreds of thousands of known members. Characterizing conserved residues within a conserved domain can identify functions shared by all family members. However, a general strategy to assess features that differ between members of a family is lacking. Fully exploring the impact of just two variable positions within a conserved domain could require assessment of 400 (i.e., 20 × 20) variants. Instead, we created and analyzed a nonredundant database of receiver domain sequences. Five percent of D + 2/T + 2 pairs were sufficient to represent 50% of receiver domain sequences. Using protein sequence analysis to prioritize mutant choice made it experimentally feasible to extensively probe the influence of positions D + 2 and T + 2 on receiver domain autodephosphorylation kinetics.
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17
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Czarnecka-Verner E, Salem TA, Gurley WB. Adaptation of the Agrobacterium tumefaciens VirG response regulator to activate transcription in plants. PLANT MOLECULAR BIOLOGY 2016; 90:217-31. [PMID: 26646288 DOI: 10.1007/s11103-015-0407-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 11/11/2015] [Indexed: 06/05/2023]
Abstract
The Agrobacterium tumefaciens VirG response regulator of the VirA/VirG two-component system was adapted to function in tobacco protoplasts. The subcellular localization of VirG and VirA proteins transiently expressed in onion cells was determined using GFP fusions. Preliminary studies using Gal4DBD-VP16 fusions with VirG and Escherichia coli UhpA, and NarL response regulators indicated compatibility of these bacterial proteins with the eukaryotic transcriptional apparatus. A strong transcriptional activator based on tandem activation domains from the Drosophila fushi tarazu and Herpes simplex VP16 was created. Selected configurations of the two-site Gal4-vir box GUS reporters were activated by chimeric effectors dependent on either the yeast Gal4 DNA-binding domain or that of VirG. Transcriptional induction of the GUS reporter was highest for the VirE19-element promoter with both constitutive and wild-type VirG-tandem activation domain effectors. Multiple VirE19 elements increased the reporter activity proportionately, indicating that the VirG DNA binding domain was functional in plants. The VirG constitutive-Q-VP16 effector was more active than the VirG wild-type. In both the constitutive and wild-type forms of VirG, Q-VP16 activated transcription of the GUS reporter best when located at the C-terminus, i.e. juxtaposed to the VirG DNA binding domain. These results demonstrate the possibility of using DNA binding domains from bacterial response regulators and their cognate binding elements in the engineering of plant gene expression.
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Affiliation(s)
- Eva Czarnecka-Verner
- Department of Microbiology and Cell Science, Program of Plant Molecular and Cellular Biology, University of Florida, Bldg. 981, 1355 Museum Drive, P.O. Box 110700, Gainesville, FL, 32611-0700, USA.
| | - Tarek A Salem
- Department of Microbiology and Cell Science, Program of Plant Molecular and Cellular Biology, University of Florida, Bldg. 981, 1355 Museum Drive, P.O. Box 110700, Gainesville, FL, 32611-0700, USA
- Molecular Biology Department, Genetic Engineering and Biotechnology Institute, University of Sadat City, Sadat City, Egypt
| | - William B Gurley
- Department of Microbiology and Cell Science, Program of Plant Molecular and Cellular Biology, University of Florida, Bldg. 981, 1355 Museum Drive, P.O. Box 110700, Gainesville, FL, 32611-0700, USA.
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18
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Page SC, Silversmith RE, Collins EJ, Bourret RB. Imidazole as a Small Molecule Analogue in Two-Component Signal Transduction. Biochemistry 2015; 54:7248-60. [PMID: 26569142 DOI: 10.1021/acs.biochem.5b01082] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
In two-component signal transduction systems (TCSs), responses to stimuli are mediated through phosphotransfer between protein components. Canonical TCSs use His → Asp phosphotransfer in which phosphoryl groups are transferred from a conserved His on a sensory histidine kinase (HK) to a conserved Asp on a response regulator (RR). RRs contain the catalytic core of His → Asp phosphotransfer, evidenced by the ability of RRs to autophosphorylate with small molecule analogues of phospho-His proteins. Phosphorelays are a more complex variation of TCSs that additionally utilize Asp → His phosphotransfer through the use of an additional component, the histidine-containing phosphotransfer domain (Hpt), which reacts with RRs both as phosphodonors and phosphoacceptors. Here we show that imidazole has features of a rudimentary Hpt. Imidazole acted as a nucleophile and attacked phosphorylated RRs (RR-P) to produce monophosphoimidazole (MPI) and unphosphorylated RR. Phosphotransfer from RR-P to imidazole required the intact RR active site, indicating that the RR provided the core catalytic machinery for Asp → His phosphotransfer. Imidazole functioned in an artificial phosphorelay to transfer phosphoryl groups between unrelated RRs. The X-ray crystal structure of an activated RR·imidazole complex showed imidazole oriented in the RR active site similarly to the His of an Hpt. Imidazole interacted with RR nonconserved active site residues, which influenced the relative reactivity of RR-P with imidazole versus water. Rate constants for reaction of imidazole or MPI with chimeric RRs suggested that the RR active site contributes to the kinetic preferences exhibited by the YPD1 Hpt.
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Affiliation(s)
- Stephani C Page
- Department of Biochemistry & Biophysics, University of North Carolina , Chapel Hill, North Carolina 27599-7260, United States
| | - Ruth E Silversmith
- Department of Microbiology & Immunology, University of North Carolina , Chapel Hill, North Carolina 27599-7290, United States
| | - Edward J Collins
- Department of Biochemistry & Biophysics, University of North Carolina , Chapel Hill, North Carolina 27599-7260, United States.,Department of Microbiology & Immunology, University of North Carolina , Chapel Hill, North Carolina 27599-7290, United States
| | - Robert B Bourret
- Department of Microbiology & Immunology, University of North Carolina , Chapel Hill, North Carolina 27599-7290, United States
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19
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Fernández I, Otero LH, Klinke S, Carrica MDC, Goldbaum FA. Snapshots of Conformational Changes Shed Light into the NtrX Receiver Domain Signal Transduction Mechanism. J Mol Biol 2015; 427:3258-3272. [DOI: 10.1016/j.jmb.2015.06.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 05/11/2015] [Accepted: 06/17/2015] [Indexed: 11/29/2022]
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20
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Cross Talk Inhibition Nullified by a Receiver Domain Missense Substitution. J Bacteriol 2015; 197:3294-306. [PMID: 26260457 DOI: 10.1128/jb.00436-15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 08/03/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED In two-component signal transduction, a sensor protein transmitter module controls cognate receiver domain phosphorylation. Most receiver domain sequences contain a small residue (Gly or Ala) at position T + 1 just distal to the essential Thr or Ser residue that forms part of the active site. However, some members of the NarL receiver subfamily have a large hydrophobic residue at position T + 1. Our laboratory previously isolated a NarL mutant in which the T + 1 residue Val-88 was replaced with an orthodox small Ala. This NarL V88A mutant confers a striking phenotype in which high-level target operon expression is both signal (nitrate) and sensor (NarX and NarQ) independent. This suggests that the NarL V88A protein is phosphorylated by cross talk from noncognate sources. Although cross talk was enhanced in ackA null strains that accumulate acetyl phosphate, it persisted in pta ackA double null strains that cannot synthesize this compound and was observed also in narL(+) strains. This indicates that acetate metabolism has complex roles in mediating NarL cross talk. Contrariwise, cross talk was sharply diminished in an arcB barA double null strain, suggesting that the encoded sensors contribute substantially to NarL V88A cross talk. Separately, the V88A substitution altered the in vitro rates of NarL autodephosphorylation and transmitter-stimulated dephosphorylation and decreased affinity for the cognate sensor, NarX. Together, these experiments show that the residue at position T + 1 can strongly influence two distinct aspects of receiver domain function, the autodephosphorylation rate and cross talk inhibition. IMPORTANCE Many bacterial species contain a dozen or more discrete sensor-response regulator two-component systems that convert a specific input into a distinct output pattern. Cross talk, the unwanted transfer of signals between circuits, occurs when a response regulator is phosphorylated inappropriately from a noncognate source. Cross talk is inhibited in part by the high interaction specificity between cognate sensor-response regulator pairs. This study shows that a relatively subtle missense change from Val to Ala nullifies cross talk inhibition, enabling at least two noncognate sensors to enforce an inappropriate output independently of the relevant input.
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21
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Immormino RM, Starbird CA, Silversmith RE, Bourret RB. Probing Mechanistic Similarities between Response Regulator Signaling Proteins and Haloacid Dehalogenase Phosphatases. Biochemistry 2015; 54:3514-27. [PMID: 25928369 DOI: 10.1021/acs.biochem.5b00286] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Response regulator signaling proteins and phosphatases of the haloacid dehalogenase (HAD) superfamily share strikingly similar folds, active site geometries, and reaction chemistry. Proteins from both families catalyze the transfer of a phosphoryl group from a substrate to one of their own aspartyl residues, and subsequent hydrolysis of the phosphoprotein. Notable differences include an additional Asp that functions as an acid/base catalyst and an active site well-structured prior to phosphorylation in HAD phosphatases. Both features contribute to reactions substantially faster than those for response regulators. To investigate mechanisms underlying the functional differences between response regulators and HAD phosphatases, we characterized five double mutants of the response regulator CheY designed to mimic HAD phosphatases. Each mutant contained the extra Asp paired with a phosphatase-inspired substitution to potentially position the Asp properly. Only CheY DR (Arg as the anchor) exhibited enhanced rates of both autophosphorylation with phosphoramidate and autodephosphorylation compared to those of wild-type CheY. Crystal structures of CheY DR complexed with MoO4(2-) or WO4(2-) revealed active site hydrogen bonding networks similar to those in HAD·substrate complexes, with the extra Asp positioned for direct interaction with the leaving group (phosphorylation) or nucleophile (dephosphorylation). However, CheY DR reaction kinetics did not exhibit the pH sensitivities expected for acid/base catalysis. Biochemical analysis indicated CheY DR had an enhanced propensity to adopt the active conformation without phosphorylation, but a crystal structure revealed unphosphorylated CheY DR was not locked in the active conformation. Thus, the enhanced reactivity of CheY DR reflected partial acquisition of catalytic and structural features of HAD phosphatases.
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Affiliation(s)
- Robert M Immormino
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina 27599-7290, United States
| | - Chrystal A Starbird
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina 27599-7290, United States
| | - Ruth E Silversmith
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina 27599-7290, United States
| | - Robert B Bourret
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina 27599-7290, United States
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22
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Fraiberg M, Afanzar O, Cassidy CK, Gabashvili A, Schulten K, Levin Y, Eisenbach M. CheY's acetylation sites responsible for generating clockwise flagellar rotation in Escherichia coli. Mol Microbiol 2014; 95:231-44. [PMID: 25388160 DOI: 10.1111/mmi.12858] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/06/2014] [Indexed: 11/30/2022]
Abstract
Stimulation of Escherichia coli with acetate elevates the acetylation level of the chemotaxis response regulator CheY. This elevation, in an unknown mechanism, activates CheY to generate clockwise rotation. Here, using quantitative selective reaction monitoring mass spectrometry and high-resolution targeted mass spectrometry, we identified K91 and K109 as the major sites whose acetylation level in vivo increases in response to acetate. Employing single and multiple lysine replacements in CheY, we found that K91 and K109 are also the sites mainly responsible for acetate-dependent clockwise generation. Furthermore, we showed that clockwise rotation is repressed when residue K91 is nonmodified, as evidenced by an increased ability of CheY to generate clockwise rotation when K91 was acetylated or replaced by specific amino acids. Using molecular dynamics simulations, we show that K91 repression is manifested in the conformational dynamics of the β4α4 loop, shifted toward an active state upon mutation. Removal of β4α4 loop repression may represent a general activation mechanism in CheY, pertaining also to the canonical phosphorylation activation pathway as suggested by crystal structures of active and inactive CheY from Thermotoga maritima. By way of elimination, we further suggest that K109 acetylation is actively involved in generating clockwise rotation.
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Affiliation(s)
- Milana Fraiberg
- Department of Biological Chemistry, The Weizmann Institute of Science, 7610001, Rehovot, Israel
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23
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Josenhans C, Jung K, Rao CV, Wolfe AJ. A tale of two machines: a review of the BLAST meeting, Tucson, AZ, 20-24 January 2013. Mol Microbiol 2013; 91:6-25. [PMID: 24125587 DOI: 10.1111/mmi.12427] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2013] [Indexed: 01/06/2023]
Abstract
Since its inception, Bacterial Locomotion and Signal Transduction (BLAST) meetings have been the place to exchange and share the latest developments in the field of bacterial signal transduction and motility. At the 12th BLAST meeting, held last January in Tucson, AZ, researchers from all over the world met to report and discuss progress in diverse aspects of the field. The majority of these advances, however, came at the level of atomic level structures and their associated mechanisms. This was especially true of the biological machines that sense and respond to environmental changes.
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Affiliation(s)
- Christine Josenhans
- Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg Strasse 1, 30625, Hannover, Germany
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24
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Creager-Allen RL, Silversmith RE, Bourret RB. A link between dimerization and autophosphorylation of the response regulator PhoB. J Biol Chem 2013; 288:21755-69. [PMID: 23760278 DOI: 10.1074/jbc.m113.471763] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Response regulator proteins within two-component signal transduction systems are activated by phosphorylation and can catalyze their own covalent phosphorylation using small molecule phosphodonors. To date, comprehensive kinetic characterization of response regulator autophosphorylation is limited to CheY, which follows a simple model of phosphodonor binding followed by phosphorylation. We characterized autophosphorylation of the response regulator PhoB, known to dimerize upon phosphorylation. In contrast to CheY, PhoB time traces exhibited an initial lag phase and gave apparent pseudo-first order rate constants that increased with protein concentration. Furthermore, plots of the apparent autophosphorylation rate constant versus phosphodonor concentration were sigmoidal, as were PhoB binding isotherms for the phosphoryl group analog BeF3(-). Successful mathematical modeling of the kinetic data necessitated inclusion of the formation of a PhoB heterodimer (one phosphorylated and one unphosphorylated monomer) with an enhanced rate of phosphorylation. Specifically, dimerization constants for the PhoB heterodimer and homodimer (two phosphorylated monomers) were similar, but the rate constant for heterodimer phosphorylation was ~10-fold higher than for the monomer. In a test of the model, disruption of the known PhoB(N) dimerization interface by mutation led to markedly slower and noncooperative autophosphorylation kinetics. Furthermore, phosphotransfer from the sensor kinase PhoR was enhanced by dimer formation. Phosphorylation-mediated dimerization allows many response regulators to bind to tandem DNA-binding sites and regulate transcription. Our data challenge the notion that response regulator dimers primarily form between two phosphorylated monomers and raise the possibility that response regulator heterodimers containing one phosphoryl group may participate in gene regulation.
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Affiliation(s)
- Rachel L Creager-Allen
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7290, USA
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