Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.13.3 (histidine kinase)
 2,405 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe the solution structures of two- and three-domain constructs of the sensor histidine kinase PrrB from Mycobacterium tuberculosis, which allow us to locate the HAMP linker relative to the ATP binding and dimerization domains. We show that the three-domain construct is active both for autophosphorylation and for phosphotransfer to the cognate response regulator, PrrA. We also describe the high-resolution crystal structure of the catalytic domain alone, and we show that, in solution, it binds ATP. The conformational flexibility of this domain is discussed and related to other structural information.
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PMID:Structural and functional aspects of the sensor histidine kinase PrrB from Mycobacterium tuberculosis. 1647 47

Two-component systems (TCSs) are the major signalling pathway in bacteria and represent potential drug targets. Among the 11 paired TCS proteins present in Mycobacterium tuberculosis H37Rv, the histidine kinases (HKs) Rv0600c (HK1) and Rv0601c (HK2) are annotated to phosphorylate one response regulator (RR) Rv0602c (TcrA). We wanted to establish the sequence-structure-function relationship to elucidate the mechanism of phosphotransfer using in silico methods. Sequence alignments and codon usage analysis showed that the two domains encoded by a single gene in homologous HKs have been separated into individual open-reading frames in M. tuberculosis. This is the first example where two incomplete HKs are involved in phosphorylating a single RR. The model shows that HK2 is a unique histidine phosphotransfer (HPt)-mono-domain protein, not found as lone protein in other bacteria. The secondary structure of HKs was confirmed using "far-UV" circular dichroism study of purified proteins. We propose that HK1 phosphorylates HK2 at the conserved H131 and the phosphoryl group is then transferred to D73 of TcrA.
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PMID:Functional insights from the molecular modelling of a novel two-component system. 1665 Aug 22

A unique three protein two-component system is present in Mycobacterium tuberculosis comprising of two histidine kinases (Rv0600c/HK1 and Rv0601c/HK2) and a response regulator (Rv0602c/TcrA). The HK2 is a novel HPt-mono domain protein absent in other bacteria. We present here the temperature and urea induced denaturation study of HK1 and HK2 using circular dichroism and fluorescence spectroscopy. HK1 and HK2 are thermally quite stable. Thermal transition of HK1 is a two-state process and that of HK2 is a three-state process. Urea denaturation of HK1 and HK2 is a three-state and two-state process, respectively. The DeltaG degrees of the two transitions during urea induced unfolding of HK1 is 4.76+/-0.6 kcal/mol and -7.11+/-0.8 kcal/mol. Unfolding of HK2 in presence of urea has DeltaG degrees of 4.766+/-0.5 kcal/mol. The intrinsic fluorescence study of HK2 unfolding implies flexibility of proline rich loop in the tryptophan bearing HAMP domain.
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PMID:Temperature and urea induced conformational changes of the histidine kinases from Mycobacterium tuberculosis. 1733 92

Two-component systems are important constituents of bacterial regulatory networks. Results of this investigation into the role of the MprAB two-component system of Mycobacterium tuberculosis indicate that it is associated with the regulation of several stress-responsive regulons. Using a deletion mutant lacking portions of the response regulator, MprA, and the histidine kinase, MprB, it was demonstrated by real-time PCR, primer extension analyses and DNA microarrays that MprAB activates sigma factor genes sigE and sigB, under SDS stress and during exponential growth. SDS-inducible, MprA-dependent transcriptional start points were identified for mprA, sigE and sigB, and variations in distance between these points and MprA-binding sites suggest that MprA is involved in different mechanisms of promoter activation. Although most of the SigE regulon was downregulated in the deletion mutant, the cluster of genes Rv1129c, Rv1130 and Rv1131, which is associated with growth in monocytes, was upregulated in the deletion mutant under SDS stress, and this upregulation was dependent upon atmospheric growth conditions. Multiple stress-associated genes of the DosR, SigD and IdeR regulons were also upregulated in the deletion mutant, during exponential growth and/or in the presence of SDS. Surprisingly, the deletion mutant had increased resistance to SDS compared to the parental strain, and enhanced growth in human peripheral blood monocytes, characteristics which may result from a loss of repression of stress-associated genes.
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PMID:Evidence for complex interactions of stress-associated regulons in an mprAB deletion mutant of Mycobacterium tuberculosis. 1737 32

The two-component signal transduction system from Mycobacterium tuberculosis bears a unique three-protein system comprising of two putative histidine kinases (HK1 and HK2) and one response regulator TcrA. By sequence analysis, HK1 is found to be an adenosine 5'-triphosphate (ATP) binding protein, similar to the nucleotide-binding domain of homologous histidine kinases, and HK2 is a unique histidine containing phosphotransfer (HPt)-mono-domain protein. HK1 is expected to interact with and phosphorylate HK2. Here, we show that HK1 binds 2'(3')-O-(2,4,6-trinitrophenyl)adenosine 5'-triphosphate monolithium trisodium salt and ATP with a 1:1 stoichiometric ratio. The ATPase activity of HK1 in the presence of HK2 was measured, and phosphorylation experiments suggested that HK1 acts as a functional kinase and phosphorylates HK2 by interacting with it. Further phosphorylation studies showed transfer of a phosphoryl group from HK2 to the response regulator TcrA. These results indicate a new mode of interaction for phosphotransfer between the two-component system proteins in bacteria.
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PMID:Probing the nucleotide binding and phosphorylation by the histidine kinase of a novel three-protein two-component system from Mycobacterium tuberculosis. 1743 92

DevS is the sensor of the DevS-DevR two-component regulatory system of Mycobacterium tuberculosis. This system is thought to be responsible for initiating entrance of this bacterium into the nonreplicating persistent state in response to NO and anaerobiosis. DevS is modular in nature and consists of two N-terminal GAF domains and C-terminal histidine kinase and ATPase domains. The first GAF domain (GAF A) binds heme, and this cofactor is thought to be responsible for sensing environmental stimuli, but the function of the second GAF domain (GAF B) is unknown. Here we report the RR characterization of full-length DevS (FL DevS) as well as truncated proteins consisting of the single GAF A domain (GAF A DevS) and both GAF domains (GAF A/B) in both oxidation states and bound to the exogenous ligands CO, NO, and O2. The results indicate that the GAF B domain increases the specificity with which the distal heme pocket of the GAF A domain interacts with CO and NO as opposed to O2. Specifically, while two comparable populations of CO and NO adducts are observed in GAF A DevS, only one of these two conformers is present in significant concentration in the GAF A/B and FL DevS proteins. In contrast, hydrogen bond interactions at the bound oxygen in the oxy complexes are conserved in all DevS constructs. The comparison of the data obtained with the O2 complexes with those of the CO and NO complexes suggests a model for ligand discrimination which relies on a specific hydrogen-bonding network with bound O2. It also suggests that interactions between the two GAF domains are responsible for transduction of structural changes at the heme domain that accompany ligand binding/dissociation to modulate activity at the kinase domain.
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PMID:Interdomain interactions within the two-component heme-based sensor DevS from Mycobacterium tuberculosis. 1767 68

Mycobacterium tuberculosis is known to transform into the nonreplicating persistence state under the influence of hypoxia or nitric oxide. DevS-DevR is a two-component regulatory system that mediates the genetic response for the transformation. DevS is a histidine kinase that contains two GAF domains for sensing hypoxia or nitric oxide. The second GAF from M. smegmatis DevS was crystallized using the sitting-drop vapour-diffusion method in the presence of sodium citrate and 2-propanol as precipitants. X-ray diffraction data were collected from crystals containing selenomethionine to a maximum resolution of 2.0 A on a synchrotron beamline. The crystals belong to the hexagonal space group P6(1). The asymmetric unit contains one molecule, corresponding to a packing density of 2.5 A(3) Da(-1). The selenium substructure was determined by the single anomalous dispersion method and structure refinement is in progress.
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PMID:Crystallization and preliminary crystallographic analysis of the second GAF domain of DevS from Mycobacterium smegmatis. 1839 25

The DevS histidine kinase of Mycobacterium smegmatis contains tandem GAF domains (GAF-A and GAF-B) in its N-terminal sensory domain. The heme iron of DevS is in the ferrous state when purified and is resistant to autooxidation from a ferrous to a ferric state in the presence of O(2). The redox property of the heme and the results of sequence comparison analysis indicate that DevS of M. smegmatis is more closely related to DosT of Mycobacterium tuberculosis than DevS of M. tuberculosis. The binding of O(2) to the deoxyferrous heme led to a decrease in the autokinase activity of DevS, whereas NO binding did not. The regulation of DevS autokinase activity in response to O(2) and NO was not observed in the DevS derivatives lacking its heme, indicating that the ligand-binding state of the heme plays an important role in the regulation of DevS kinase activity. The redox state of the quinone/quinol pool of the respiratory electron transport chain appears not to be implicated in the regulation of DevS activity. Neither cyclic GMP (cGMP) nor cAMP affected DevS autokinase activity, excluding the possibility that the cyclic nucleotides serve as the effector molecules to modulate DevS kinase activity. The three-dimensional structure of the putative GAF-B domain revealed that it has a GAF folding structure without cyclic nucleotide binding capacity.
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PMID:O2- and NO-sensing mechanism through the DevSR two-component system in Mycobacterium smegmatis. 1870 94

The attenuated Mycobacterium tuberculosis H37Ra strain is an isogenic counterpart of the virulent paradigm strain H37Rv. Recently, a link between a point mutation in the PhoP transcriptional regulator and avirulence of H37Ra was established. Remarkably, a previous study demonstrated negative autoregulation of the phoP gene in H37Ra. These findings led us to study the transcriptional autoregulation of PhoP in the virulent H37Rv strain. In contrast to the negative autoregulation of PhoP previously published for H37Ra, our experiments using a phoP promoter-lacZ fusion showed that PhoP is positively autoregulated in both H37Rv and H37Ra compared with an H37Rv phoP deletion mutant constructed in this study. Using quantitative reverse transcription-PCR (RT-PCR) analysis, we showed that the phoP gene is transcribed at similar levels in H37Rv and H37Ra. Gel mobility shift and DNase I footprinting assays allowed us to identify the precise binding region of PhoP from H37Rv to the phoP promoter. We also carried out RT-PCR studies to demonstrate that phoP is transcribed together with the adjacent gene phoR, which codes for the cognate histidine kinase of the phoPR two-component system. In addition, quantitative RT-PCR studies showed that phoR is independently transcribed from a promoter possibly regulated by PhoP. Finally, we discuss the possible role in virulence of a single point mutation found in the phoP gene from the attenuated H37Ra strain but not in virulent members of the M. tuberculosis complex.
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PMID:The Mycobacterium tuberculosis phoPR operon is positively autoregulated in the virulent strain H37Rv. 1875 48

Two-component signal transduction pathways comprising a histidine kinase and its cognate response regulator play a dominant role in the adaptation of Mycobacterium tuberculosis to its host, and its virulence, pathogenicity and latency. Autophosphorylation occurs at a conserved histidine of the histidine kinase and subsequently the phosphoryl group is transferred to the conserved aspartate of its cognate response regulator. Among the twelve two-component systems of M. tuberculosis, Rv0600c (HK1), Rv0601c (HK2) and Rv0602c (TcrA) are annotated as a unique three-protein two-component system. HK1 contains an ATP-binding domain, and HK2, a novel Hpt mono-domain protein, contains the conserved phosphorylable histidine residue. HK1 and HK2 complement each other's functions. Interactions among different domains of the HK1, HK2 and TcrA proteins were studied using a yeast two-hybrid system. Self-interaction was observed for HK2 but not for HK1 or TcrA. HK2 was found to interact reasonably well with both HK1 and TcrA, but HK1 interacted weakly with TcrA. The conserved aspartate-containing receiver domain of TcrA interacted well with HK2 but not with HK1. These results suggest the existence of a novel signalling mechanism amongst HK1-HK2-TcrA, and a model for this mechanism is proposed.
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PMID:Intra- and intermolecular domain interactions among novel two-component system proteins coded by Rv0600c, Rv0601c and Rv0602c of Mycobacterium tuberculosis. 1924 48


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