Secondary literature sources for HAMP
The following references were automatically generated.
- Beel BD, Hazelbauer GL
- Substitutions in the periplasmic domain of low-abundance chemoreceptor trg that induce or reduce transmembrane signaling: kinase activation and context effects.
- J Bacteriol. 2001; 183: 671-9
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We extended characterization of mutational substitutions in the ligand-binding region of Trg, a low-abundance chemoreceptor of Escherichia coli. Previous investigations using patterns of adaptational methylation in vivo led to the suggestion that one class of substitutions made the receptor insensitive, reducing ligand-induced signaling, and another mimicked ligand occupancy, inducing signaling in the absence of ligand. We tested these deductions with in vitro assays of kinase activation and found that insensitive receptors activated the kinase as effectively as wild-type receptors and that induced-signaling receptors exhibited the low level of kinase activation characteristic of occupied receptors. Differential activation by the two mutant classes was not dependent on high-abundance receptors. Cellular context can affect the function of low-abundance receptors. Assays of chemotactic response and adaptational modification in vivo showed that increasing cellular dosage of mutant forms of Trg to a high-abundance level did not significantly alter phenotypes, nor did the presence of high-abundance receptors significantly correct phenotypic defects of reduced-signaling receptors. In contrast, defects of induced-signaling receptors were suppressed by the presence of high-abundance receptors. Grafting the interaction site for the adaptational-modification enzymes to the carboxyl terminus of induced-signaling receptors resulted in a similar suppression of phenotypic defects of induced-signaling receptors, implying that high-abundance receptors could suppress defects in induced-signaling receptors by providing their natural enzyme interaction sites in trans in clusters of suppressing and suppressed receptors. As in the case of cluster-related functional assistance provided by high-abundance receptors for wild-type low-abundance receptors, suppression by high-abundance receptors of phenotypic defects in induced-signaling forms of Trg involved assistance in adaptation, not signaling.
- Ma XJ
- Cell-cycle regulatory proteins Hsl7p/Skb1p belong to the protein methyltransferase superfamily.
- Trends Biochem Sci. 2000; 25: 11-2
- Toyoda-Yamamoto A, Shimoda N, Machida Y
- Genetic analysis of the signal-sensing region of the histidine protein kinase VirA of Agrobacterium tumefaciens.
- Mol Gen Genet. 2000; 263: 939-47
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The membrane-bound sensor protein kinase VirA of Agrobacterium tumefaciens detects plant phenolic substances, which induce expression of vir genes that are essential for the formation of the crown gall tumor. VirA also responds to specific monosaccharides, which enhance vir expression. These sugars are sensed by the periplasmic domain of VirA that includes the region homologous to the chemoreceptor Trg, and the phenolics are thought to be detected by a part of the cytoplasmic linker domain, while the second transmembrane domain (TM2) is reported to be nonessential. To define regions of VirA that are essential for signal sensing, we introduced base-substitution and deletion mutations into coding regions that are conserved among the respective domains of VirA proteins from various Agrobacterium strains, and examined the effects of these mutations on vir induction and tumorigenicity. The results show that the Trg-homologous region in the periplasmic domain is not essential for the enhancement of vir gene expression by sugars. Most mutations in the TM2 domain also failed to influence enhancement by sugars and reduced the level of vir induction, but a mutation in the TM2 region adjacent to the cytoplasmic linker abolished induction of the vir genes. In the linker domain, sites essential for vir induction by phenolics were scattered over the entire region. We propose that a topological feature formed by the linker domain and at least part of the TM2 may be crucial for activation of a membrane-anchored VirA protein. Complementation analysis with two different VirA mutants suggested that intermolecular phosphorylation between VirA molecules occurs in vivo, and that two intact periplasmic regions in a VirA dimer are required for the enhancement of vir induction by sugars.
- Falke JJ, Kim SH
- Structure of a conserved receptor domain that regulates kinase activity: the cytoplasmic domain of bacterial taxis receptors.
- Curr Opin Struct Biol. 2000; 10: 462-9
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Many bacteria are motile and use a conserved class of transmembrane sensory receptor to regulate cellular taxis toward an optimal living environment. These conserved receptors are typically stimulated by extracellular signals, but also undergo adaptation via covalent modification at specific sites on their cytoplasmic domains. The function of the cytoplasmic domain is to integrate the extracellular and adaptive signals, and to use this integrated information to regulate an associated histidine kinase. The kinase, in turn, triggers a cytoplasmic phosphorylation pathway of the two-component class. The high-resolution structure of a receptor cytoplasmic domain has recently been determined by crystallographic methods and is largely consistent with a structural model independently generated by chemical studies of the domain in the full-length, membrane-bound receptor. These results represent an important step toward a mechanistic understanding of receptor-to-kinase information transfer.
- Doering CB, Danner DJ
- Expression of murine branched-chain alpha-keto acid dehydrogenase kinase.
- Methods Enzymol. 2000; 324: 491-7
- Virginia M, Appleyard CL, McPheat WL, Stark MJ
- A novel 'two-component' protein containing histidine kinase and response regulator domains required for sporulation in Aspergillus nidulans.
- Curr Genet. 2000; 37: 364-72
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We have characterised a-novel Aspergillus nidulans gene encoding a 'two-component' signalling protein (tcsA). tcsA encodes both a histidine kinase domain and a response regulator domain similar to those found in bacterial, lower eukaryotic and plant members of the two-component family of proteins, while two PAS domains in the amino-terminal region of the predicted tcsA product may monitor the signal which regulates a tcsA histidine kinase-response regulator phosphorelay. While tcsA is nonessential for vegetative growth, cells lacking the gene are unable to produce conidia on standard Aspergillus growth media. However, tcsA is not absolutely required for production since this defect is suppressed by growth on 1 M sorbitol.
- Hoch JA
- Two-component and phosphorelay signal transduction.
- Curr Opin Microbiol. 2000; 3: 165-70
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Two-component and phosphorelay signal transduction systems are the major means by which bacteria recognize and respond to a variety of environmental stimuli. Recent results have implicated these systems in the regulation of a variety of essential processes including cell-cycle progression, pathogenicity, and developmental pathways. Elucidation of the structures of the interacting domains is leading to an understanding of the mechanisms of molecular recognition and phosphotransfer in these systems.
- Beier D, Frank R
- Molecular characterization of two-component systems of Helicobacter pylori.
- J Bacteriol. 2000; 182: 2068-76
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Two-component systems are frequently involved in the adaptation of bacteria to changing environmental conditions at the level of transcriptional regulation. Here we report the characterization of members of the two-component systems of the gastric pathogen Helicobacter pylori deduced from the genome sequence of strain 26695. We demonstrate that the response regulators HP166, HP1043, and HP1021 have essential functions, as disruption of the corresponding genes is lethal for the bacteria, irrespective of the fact that HP1043 and HP1021 have nonconserved substitutions in crucial amino acids of their receiver domains. An analysis of the in vitro phosphorylation properties of the two-component proteins demonstrates that HP244-HP703 and HP165-HP166 are cognate histidine kinase-response regulator pairs. Furthermore, we provide evidence that the variability of the histidine kinase HP165 caused by a poly(C) tract of variable length close to the 3' end of open reading frame 165/164 does not interfere with the kinase activity of the transmitter domain of HP165.
- Matsushika A, Mizuno T
- Characterization of three putative sub-domains in the signal-input domain of the ArcB hybrid sensor in Escherichia coli(1).
- J Biochem (Tokyo). 2000; 127: 855-60
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The ArcB sensor plays a crucial role in the histidine to aspartate (His-to-Asp) phosphorelay signal transduction, which is involved in the transcriptional regulatory network that allows Escherichia coli cells to sense various respiratory growth conditions. ArcB is one of the best-studied hybrid His-kinases involved in the multi-step His-to-Asp phosphorelay. However, a major question that remains to be elucidated is: how does ArcB sense an anoxic signal? The N-terminal region of ArcB is considered to be a signal-input domain, which probably plays a role in such signal-perception. In this study, this N-terminal region of ArcB was dissected into three putative sub-domains, a "transmembrane domain," a "leucine-zipper-like domain, " and a "PAS-like domain." The importance of these structural domains was assessed in vivo and in vitro by systematically analyzing a number of arcB mutants, each of which encodes a mutant ArcB protein having an amino acid substitution or a deletion within one of these sub-domains. The results are discussed with special reference to the nature of the ArcB anaerobic sensor.
- Delaroque N, Wolf S, Muller DG, Knippers R
- The brown algal virus EsV-1 particle contains a putative hybrid histidine kinase.
- Virology. 2000; 273: 383-90
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The Ectocarpus siliculosus virus, EsV-1, occurs worldwide in all populations of the filamentous marine brown alga E. siliculosus. We have screened an expression library of EsV-1 restriction fragments and identified a DNA clone with the potential to code for a 52-kDa histidine protein kinase. The derived amino acid sequence includes all homology boxes diagnostic for histidine protein kinases and, in addition, amino acid motifs that are commonly found in response regulators of bacterial two-component signal transduction proteins. Thus, the novel viral protein can be classified as a hybrid histidine protein kinase of a type that has previously been detected in fungi, slime molds, and plants. By using purified antibodies, we found that the protein with its potential kinase activity is located on the outer shell of viral particles. This is the first report on a two-component regulator-like protein in viruses and could provide the basis for speculations with regard to the evolution of EsV-1 and related viruses.
- Brenner C, Bieganowski P, Pace HC, Huebner K
- The histidine triad superfamily of nucleotide-binding proteins.
- J Cell Physiol. 1999; 181: 179-87
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Histidine triad (HIT) proteins were until recently a superfamily of proteins that shared only sequence motifs. Crystal structures of nucleotide-bound forms of histidine triad nucleotide-binding protein (Hint) demonstrated that the conserved residues in HIT proteins are responsible for their distinctive, dimeric, 10-stranded half-barrel structures that form two identical purine nucleotide-binding sites. Hint-related proteins, found in all forms of life, and fragile histidine triad (Fhit)-related proteins, found in animals and fungi, represent the two main branches of the HIT superfamily. Hint homologs are intracellular receptors for purine mononucleotides whose cellular function remains elusive. Fhit homologs bind and cleave diadenosine polyphosphates (Ap(n)A) such as ApppA and AppppA. Fhit-Ap(n)A complexes appear to function in a proapoptotic tumor suppression pathway in epithelial tissues. In invertebrates, Fhit homologs are encoded as fusion proteins with proteins related to plant and bacterial nitrilases that are candidate signaling partners in tumor suppression.
- Mizuno T
- [His-Asp phosphotransfer signal transduction]
- Tanpakushitsu Kakusan Koso. 1999; 44: 412-20
- Lange R et al.
- Domain organization and molecular characterization of 13 two-component systems identified by genome sequencing of Streptococcus pneumoniae.
- Gene. 1999; 237: 223-34
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In bacteria, adaptive responses to environmental stimuli are often initiated by two-component signal transduction systems (TCS). The prototypical TCS comprises two proteins: a histidine kinase (HK, hk) and a response regulator (RR rr). Recent research has suggested that compounds that inhibit two-component systems might have good antibacterial activity. In order to identify TCS that are crucial for growth or virulence of Streptococcus pneumoniae, we have examined the genomic sequence of a virulent S. pneumoniae strain for genes that are related to known histidine kinases or response regulators. Altogether 13 histidine kinases and 13 response regulators have been identified. The protein sequences encoded by these genes were compared with sequences deposited in public databases. This analysis revealed that two of the 13 pneumococcal TCSs have been described before (ciaRH and comDE) and two are homologous to the yycFG and the phoRP genes of Bacillus subtilis. All the pneumococcal response regulators contain putative DNA binding motifs within the C-terminal output domain, implying that they are involved in transcriptional control. Two of these response regulators are obviously the first representatives of a new subfamily containing an AraC-type DNA-binding effector domain. To assess the regulatory role of these transcription factors, we disrupted each of the 13 response regulator genes by insertional mutagenesis. All the viable mutant strains with disrupted response regulator genes were further characterized with regard to growth in vitro, competence, and experimental virulence. Two response regulator genes could not be inactivated, indicating that they may regulate essential cellular functions. The possibility of using these systems as targets for the development of novel antibacterials will be discussed.
- Levit MN, Stock JB
- pH sensing in bacterial chemotaxis.
- Novartis Found Symp. 1999; 221: 38-50
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Bacteria are able to sense a broad range of chemical and energetic stimuli and modulate their swimming behaviour to migrate to more favourable environments. Signal transduction in bacterial chemotaxis is mediated by a two-component system composed of a protein histidine kinase, CheA, and a response regulator, CheY. The phosphorylated response regulator, P approximately CheY, binds to a protein at the flagellar motor, FliM, to cause reversals in flagellar motor rotation. The level of P approximately CheY is controlled by the activity of the kinase CheA, which is in turn regulated by membrane receptors at the cell surface. Membrane receptors such as the aspartate receptor, Tar, are composed of two distinct regions: an extracellular sensing domain that binds stimulatory ligands, aspartate in the case of Tar; and an intracellular signalling domain that forms a complex with the protein kinase CheA. What is the mechanism of transmembrane signalling? How does aspartate binding to the sensing domain at the outside surface of the membrane translate into a change in kinase activity at the membrane cytosol interface? Recent results suggest that the mechanism depends on perturbations in lateral packing within an extensive array of receptors localized to patches at the cell poles. Receptor patching appears to depend on higher-order associations with the kinase CheA as well as an adaptor protein, CheW. It is difficult to assess the locus of pH effects within the context of even a simple signal transduction system like that involved in bacterial chemotaxis. Previous results with mutant strains have indicated that the serine receptor, Tsr, is critical for pH sensing, but in vitro results do not support such a straightforward interpretation of the genetic data.
- Levit MN, Liu Y, Stock JB
- Mechanism of CheA protein kinase activation in receptor signaling complexes.
- Biochemistry. 1999; 38: 6651-8
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The chemotaxis receptor for aspartate, Tar, generates responses by regulating the activity of an associated histidine kinase, CheA. Tar is composed of an extracellular sensory domain connected by a transmembrane sequence to a cytoplasmic signaling domain. The cytoplasmic domain fused to a leucine zipper dimerization domain forms soluble active ternary complexes with CheA and an adapter protein, CheW. The kinetics of kinase activity within these complexes compared to CheA alone indicate approximately a 50% decrease in the KM for ATP and a 100-fold increase in the Vmax. A truncated CheA construct that lacks the phosphoaccepting H-domain and the CheY/CheB-binding domain forms an activated ternary complex that is similar to the one formed by the full-length CheA protein. The Vmax of H-domain phosphorylation by this complex is enhanced approximately 60-fold, the KM for ATP decreased to 50%, and the KM for H-domain decreased to 20% of the values obtained with the same CheA construct in the absence of receptor and CheW. The kinetic data support a mechanism of CheA regulation that involves perturbation of an equilibrium between an inactive form where the H-domain is loosely bound and an active form where the H-domain is tightly associated with the CheA active site and properly positioned for phosphotransfer. The data are consistent with an asymmetric mechanism of CheA activation [Levit, M., Liu, I., Surette, M. G., and Stock, J. B. (1996) J. Biol. Chem. 271, 32057-32063] wherein only one phosphoaccepting domain of CheA at a time can interact with an active center within a CheA dimer.
- Kaspar S et al.
- The periplasmic domain of the histidine autokinase CitA functions as a highly specific citrate receptor.
- Mol Microbiol. 1999; 33: 858-72
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The two-component regulatory system CitA/CitB is essential for induction of the citrate fermentation genes in Klebsiella pneumoniae. CitA represents a membrane-bound sensor kinase consisting of a periplasmic domain flanked by two transmembrane helices, a linker domain and the conserved kinase or transmitter domain. A fusion protein (MalE-CitAC) composed of the maltose-binding protein and the CitA kinase domain (amino acids 327-547) showed constitutive autokinase activity and transferred the gamma-phosphate group of ATP to its cognate response regulator CitB. The autokinase activity of CitA was abolished by an H350L exchange, and phosphorylation of CitB was inhibited by a D56N exchange, indicating that H-350 and D-56 represent the phosphorylation sites of CitA and CitB respectively. In the presence of ATP, CitB-D56N formed a stable complex with MalE-CitAC. To analyse the sensory properties of CitA, the periplasmic domain (amino acids 45-176) was overproduced as a soluble, cytoplasmic protein with a C-terminally attached histidine tag (CitAPHis). Purified CitAPHis bound citrate, but none of the other tri- and dicarboxylates tested, with high affinity (KD approximately 5 &mgr;M at pH 7) in a 1:1 stoichiometry. As shown by isothermal titration calorimetry, the binding reaction was driven by the enthalpy change (DeltaH = -76.3 kJ mol-1), whereas the entropy change was opposed (-TDeltaS = + 46.3 kJ mol-1). The pH dependency of the binding reaction indicated that the dianionic form H-citrate2- is the citrate species recognized by CitAPHis. In the presence of Mg2+ ions, the dissociation constant increased significantly, suggesting that the Mg-citrate complex is not bound by CitAPHis. This work defines the periplasmic domain of CitA as a highly specific citrate receptor and elucidates the binding characteristics of CitAPHis.
- Rhoads RE
- Signal transduction pathways that regulate eukaryotic protein synthesis.
- J Biol Chem. 1999; 274: 30337-40
- Bass RB, Falke JJ
- Detection of a conserved alpha-helix in the kinase-docking region of the aspartate receptor by cysteine and disulfide scanning.
- J Biol Chem. 1998; 273: 25006-14
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The transmembrane aspartate receptor of Escherichia coli and Salmonella typhimurium propagates extracellular signals to the cytoplasm, where its cytoplasmic domain regulates the histidine kinase, CheA. Different signaling states of the cytoplasmic domain modulate the kinase autophosphorylation rate over at least a 100-fold range. Biochemical and genetic studies have implicated a specific region of the cytoplasmic domain, termed the signaling subdomain, as the region that transmits regulation from the receptor to the kinase. Here cysteine and disulfide scanning are applied to the N-terminal half of the signaling subdomain to probe its secondary structure, solvent exposure, and protein-protein interactions. The chemical reactivities of the scanned cysteines exhibit the characteristic periodicity of an alpha-helix with distinct solvent-exposed and buried faces. This helix, termed alpha7, ranges approximately from residue 355 through 386. Activity measurements probing the effects of cysteine substitutions in vivo and in vitro reveal that both faces of helix alpha7 are critical for kinase activation, while the buried face is especially critical for kinase down-regulation. Disulfide scanning of the region suggests that helix alpha7 is not in direct contact with its symmetric partner (alpha7') from the other subunit; presently, the structural element that packs against the buried face of the helix remains unidentified. Finally, a novel approach termed "protein interactions by cysteine modification" indicates that the exposed C-terminal face of helix alpha7 provides an essential docking site for the kinase CheA or for the coupling protein CheW.
- Burton GJ, Hecht GB, Newton A
- Roles of the histidine protein kinase pleC in Caulobacter crescentus motility and chemotaxis.
- J Bacteriol. 1997; 179: 5849-53
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The Caulobacter crescentus histidine kinase genes pleC and divJ have been implicated in the regulation of polar morphogenesis and cell division, respectively. Mutations in pleC also potentiate the cell division phenotype of divJ mutations. To investigate the involvement of the PleC kinase in motility and cell cycle regulation, we carried out a pseudoreversion analysis of the divJ332 allele, which confers a temperature-sensitive motility (Mot-) phenotype. All cold-sensitive pseudorevertants with a Mot+ phenotype at 37 degrees C and a cold-sensitive swarm phenotype in soft agar at 24 degrees C contained extragenic suppressors that were null mutations mapping to pleC. Instead of a cell division defect at the nonpermissive temperature, however, revertants displayed a cold-sensitive defect in chemotaxis (Che-). In addition, the mutant cells were also supermotile, a phenotype previously associated only with mutations in the response regulator gene pleD that block the loss of motility. We also found that the Mot- defect of pleC mutants is suppressed by a pleD301/pleD+ merodiploid and results in a similar, supermotile, cold-sensitive Che- phenotype. These results implicate signal transduction pathways mediated by PleC-DivK and DivJ-PleD in the regulation of chemotaxis as well as motility. We discuss these findings and the observation that although the PleC kinase does not play an indispensable role in cell division, a temperature-sensitive allele of pleC (pleC319) has severely reduced viability under stringent growth conditions.
- Ellefson DD, Weber U, Wolfe AJ
- Genetic analysis of the catalytic domain of the chemotaxis-associated histidine kinase CheA.
- J Bacteriol. 1997; 179: 825-30
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Escherichia coli cells express two forms of CheA, the histidine kinase associated with chemotaxis. The long form, CheA(L), plays a critical role in chemotactic signal transduction by phosphorylating two chemotaxis-associated response regulators, CheY and CheB. CheA(L) first autophosphorylates amino acid His-48 before its phosphoryl group is transferred to these response regulators. The short form, CheA(S), lacks the amino-terminal 97 amino acids of CheA(L) and therefore does not possess the site of phosphorylation. The centrally located transmitter domain of both forms of CheA contains four regions, called N, G1, F, and G2, highly conserved among histidine kinases of the family of two-component signal transduction systems. On the basis of sequence similarity to highly conserved regions of certain eukaryotic kinases, the G1 and G2 regions are purported to be involved in the binding and hydrolysis of ATP. We report here that alleles mutated in the G1, G2, or F region synthesize CheA variants that cannot autophosphorylate in vitro and which cannot support chemotaxis in vivo. We also show that in vitro, the nonphosphorylatable CheA(S) protein mediates transphosphorylation of a CheA(L) variant defective in both G1 and G2. In contrast, CheA(L) variants defective for either G1 or G2 mediate transphosphorylation of each other poorly, if at all. These results are consistent with a mechanism by which the G1 and G2 regions of one protomer of a CheA dimer form a unit that mediates transphosphorylation of the other protomer within that dimer.
