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PubMed2006

The response regulator ResD modulates virulence gene expression in response to carbohydrates in Listeria monocytogenes.

Listeria monocytogenes is a versatile bacterial pathogen that is able to accommodate to diverse environmental and host conditions. Presently, we have identified a L. monocytogenes two-component response regulator, ResD that is required for the repression of virulence gene expression known to occur in the presence of easily fermentable carbohydrates not found inside host organisms. Structurally and functionally, ResD resembles the respiration regulator ResD in Bacillus subtilis as deletion of the L. monocytogenes resD reduces respiration and expression of cydA, encoding a subunit of cytochrome bd. The resD mutation also reduces expression of mptA encoding the EIIABman component of a mannose/glucose-specific PTS system, indicating that ResD controls sugar uptake. This notion was supported by the poor growth of resD mutant cells that was alleviated by excess of selected carbohydrates. Despite the growth deficient phenotype of the mutant in vitro the mutation did not affect intracellular multiplication in epithelial or macrophage cell lines. When examining virulence gene expression we observed traditional induction by charcoal in both mutant and wild-type cells whereas the repression observed in wild-type cells by fermentable carbohydrates did not occur in resD mutant cells. Thus, ResD is a central regulator of L. monocytogenes when present in the external environment.

Animals↗
PubMed1999

Identification and characterization of a two-component sensor-kinase and response-regulator system (DcuS-DcuR) controlling gene expression in response to C4-dicarboxylates in Escherichia coli.

The dcuB gene of Escherichia coli encodes an anaerobic C4-dicarboxylate transporter that is induced anaerobically by FNR, activated by the cyclic AMP receptor protein, and repressed in the presence of nitrate by NarL. In addition, dcuB expression is strongly induced by C4-dicarboxylates, suggesting the presence of a novel C4-dicarboxylate-responsive regulator in E. coli. This paper describes the isolation of a Tn10 mutant in which the 160-fold induction of dcuB expression by C4-dicarboxylates is absent. The corresponding Tn10 mutation resides in the yjdH gene, which is adjacent to the yjdG gene and close to the dcuB gene at approximately 93.5 min in the E. coli chromosome. The yjdHG genes (redesignated dcuSR) appear to constitute an operon encoding a two-component sensor-regulator system (DcuS-DcuR). A plasmid carrying the dcuSR operon restored the C4-dicarboxylate inducibility of dcuB expression in the dcuS mutant to levels exceeding those of the dcuS+ strain by approximately 1.8-fold. The dcuS mutation affected the expression of other genes with roles in C4-dicarboxylate transport or metabolism. Expression of the fumarate reductase (frdABCD) operon and the aerobic C4-dicarboxylate transporter (dctA) gene were induced 22- and 4-fold, respectively, by the DcuS-DcuR system in the presence of C4-dicarboxylates. Surprisingly, anaerobic fumarate respiratory growth of the dcuS mutant was normal. However, under aerobic conditions with C4-dicarboxylates as sole carbon sources, the mutant exhibited a growth defect resembling that of a dctA mutant. Studies employing a dcuA dcuB dcuC triple mutant unable to transport C4-dicarboxylates anaerobically revealed that C4-dicarboxylate transport is not required for C4-dicarboxylate-responsive gene regulation. This suggests that the DcuS-DcuR system responds to external substrates. Accordingly, topology studies using 14 DcuS-BlaM fusions showed that DcuS contains two putative transmembrane helices flanking a approximately 140-residue N-terminal domain apparently located in the periplasm. This topology strongly suggests that the periplasmic loop of DcuS serves as a C4-dicarboxylate sensor. The cytosolic region of DcuS (residues 203 to 543) contains two domains: a central PAS domain possibly acting as a second sensory domain and a C-terminal transmitter domain. Database searches showed that DcuS and DcuR are closely related to a subgroup of two-component sensor-regulators that includes the citrate-responsive CitA-CitB system of Klebsiella pneumoniae. DcuS is not closely related to the C4-dicarboxylate-sensing DctS or DctB protein of Rhodobacter capsulatus or rhizobial species, respectively. Although all three proteins have similar topologies and functions, and all are members of the two-component sensor-kinase family, their periplasmic domains appear to have evolved independently.

Amino Acid Sequence↗
PubMed1991

Roles of the highly conserved aspartate and lysine residues in the response regulator of bacterial chemotaxis.

The chemotactic responses of bacteria such as Escherichia coli and Salmonella typhimurium are mediated by phosphorylation of the CheY protein. Phospho-CheY interacts with the flagellar motor switch to cause tumbly behavior. CheY belongs to a large family of phosphorylated response regulators that function in bacteria to control motility and regulate gene expression. Residues corresponding to Asp57, Asp13, and Lys109 in CheY are highly conserved among all of these proteins. The site of phosphorylation in CheY is Asp57, and in the three-dimensional structure of CheY the Asp57 carboxylate side chain is in close proximity to the beta-carboxylate of Asp13 and the epsilon-amin of Lys109. To further examine the roles of these residues in response regulator function, each has been mutated to a conservative substitution. Asn for Asp and Arg for Lys. All mutations abolished CheY function in vivo. Whereas the Asp to Asn mutations dramatically reduced levels of CheY phosphorylation, the Lys to Arg mutation had the opposite effect. The high level of phosphorylation in the Lys109 mutant results from a decreased autophosphatase activity as well as a lack of phosphatase stimulation by the phosphatase activating protein, CheZ. Despite its high level of phosphorylation, the Lys109 mutant protein cannot produce tumbly behavior. Thus, Lys109 is required for an event subsequent to phosphorylation. We propose that an interaction between the epsilon-amino of Lys109 and the phosphoryl group at Asp57 is essential for the conformational switch that leads to activation of CheY.

Aspartic Acid↗
PubMed1997

The Skn7 response regulator controls gene expression in the oxidative stress response of the budding yeast Saccharomyces cerevisiae.

Deletion of the bacterial two-component response regulator homologue Skn7 results in sensitivity of yeast to oxidizing agents indicating that Skn7 is involved in the response to this type of stress. Here we demonstrate that following oxidative stress, Skn7 regulates the induction of two genes: TRX2, encoding thioredoxin, and a gene encoding thioredoxin reductase. TRX2 is already known to be induced by oxidative stress dependent on the Yap1 protein, an AP1-like transcription factor responsible for the induction of gene expression in response to various stresses. The thioredoxin reductase gene has not previously been shown to be activated by oxidative stress and, significantly, we find that it too is regulated by Yap1. The control of at least TRX2 by Skn7 is a direct mechanism as Skn7 binds to the TRX2 gene promoter in vitro. This shows Skn7 to be a transcription factor, at present the only such eukaryotic two-component signalling protein. Our data further suggest that Skn7 and Yap1 co-operate on the TRX2 promoter, to induce transcription in response to oxidative stress.

Blotting, Northern↗
PubMed2003

The SKHR motif is required for biological function of the VirR response regulator from Clostridium perfringens.

The response regulator VirR and its cognate sensor histidine kinase, VirS, are responsible for toxin gene regulation in the human pathogen Clostridium perfringens. The C-terminal domain of VirR (VirRc) contains the functional FxRxHrS motif, which is involved in DNA binding and is conserved in many regulatory proteins. VirRc was cloned, purified, and shown by in vivo and in vitro studies to comprise an independent DNA binding domain. Random and site-directed mutagenesis was used to identify further amino acids that were required for the functional integrity of the protein. Random mutagenesis identified a unique residue, Met-172, that was required for biological function. Site-directed mutagenesis of the SKHR motif (amino acids 216 to 219) revealed that these residues were also required for biological activity. Analysis of the mutated proteins indicated that they were unable to bind to the DNA target with the same efficiency as the wild-type protein.

Amino Acid Motifs↗
PubMed2002

Expression, autoregulation, and DNA binding properties of the Mycobacterium tuberculosis TrcR response regulator.

The TrcRS two-component system of Mycobacterium tuberculosis is comprised of the TrcS histidine kinase and the TrcR response regulator, which is homologous to the OmpR class of DNA binding response regulators. Reverse transcription-PCRs with total RNA showed that the trcR and trcS two-component system genes are transcribed in broth-grown M. tuberculosis. Analysis of the trcR and trcS genes using various SCOTS (selective capture of transcribed sequences) probes also confirmed that these genes are expressed in broth-grown cultures and after 18 h of M. tuberculosis growth in cultured human primary macrophages. To determine if the TrcR response regulator is autoregulated, a trcR-lacZ fusion plasmid and a TrcR expression plasmid were cotransformed into Escherichia coli. Upon induction of the TrcR protein, there was a >500-fold increase in beta-galactosidase activity from the trcR-lacZ fusion, indicating that TrcR is involved in transcriptional autoactivation. Gel mobility shift assays with the trcR promoter and TrcR established that the response regulator was autoregulating via direct binding. By use of a delimiting series of overlapping trcR PCR fragments in gel mobility shift assays with TrcR, an AT-rich region of the trcR promoter was shown to be essential for TrcR binding. Additionally, this AT-rich sequence was protected by TrcR in DNase I protection assays. To further analyze the role of the AT-rich region in TrcR autoregulation, the trcR promoter was mutated and analyzed in lacZ transcriptional fusions in the presence of TrcR. Alteration of the AT-rich sequence in the trcR promoter resulted in the loss of trcR transcriptional activation in the presence of TrcR. This report indicates that the M. tuberculosis TrcR response regulator activates its own expression by interacting with the AT-rich sequence of the trcR promoter.

Base Sequence↗
PubMed2006

Regulation of gene expression in Streptococcus pneumoniae by response regulator 09 is strain dependent.

Recent murine studies have demonstrated that the role of response regulator 09 (RR09) of Streptococcus pneumoniae in virulence is different in different strains. In the present study, we used a murine pneumonia model of infection to assess the virulence of a TIGR4 rr09 mutant, and we found that TIGR4Deltarr09 was attenuated after intranasal infection. Furthermore, we investigated the in vitro transcriptional changes in pneumococcal rr09 mutants of two strains, D39 and TIGR4, by microarray analysis. The transcriptional profiles of the rr09 mutants of both strains had clear differences compared to the profiles of the parental wild-type strains. In D39Deltarr09, but not in TIGR4Deltarr09, genes involved in competence (e.g., comAB) were upregulated. In TIGR4, genes located on the rlrA pathogenicity islet, which are not present in the D39 genome, appeared to be regulated by RR09. Furthermore, several phosphotransferase systems (PTSs) believed to be involved in sugar uptake (e.g., the PTS encoded by sp0060 to sp0066) were strongly downregulated in D39Deltarr09, while they were not regulated by RR09 in TIGR4. To examine the role of one of these PTSs in virulence, D39Deltasp0063 was constructed and tested in a murine infection model. No difference between the virulence of this strain and the virulence of the wild type was found, indicating that downregulation of the sp0063 gene alone is not the cause of the avirulent phenotype of D39Deltarr09. Finally, expression of rr09 and expression of three of our identified RR09 targets during infection in mice were assessed. This in vivo experiment confirmed that there were differences between expression in wild-type strain TIGR4 and expression in the rr09 mutant, as well as differences between expression in wild-type strain D39 and expression in wild-type strain TIGR4. In conclusion, our results indicate that there is strain-specific regulation of pneumococcal gene expression by RR09.

Animals↗
PubMed2003

Inducible bacteriocin production in Lactobacillus is regulated by differential expression of the pln operons and by two antagonizing response regulators, the activity of which is enhanced upon phosphorylation.

Expression of the five (pln) operons involved in the bacteriocin production of Lactobacillus plantarum C11 is regulated by a so-called pheromone-based signal-transducing network, in which the peptide pheromone (PlnA) induces bacteriocin production through the action of a histidine protein kinase (PlnB) and two antagonizing response regulators (PlnC as an activator and PlnD as a negative regulator). All pln-regulated promoters contain a conserved pair of direct repeats that serve as binding sites for PlnC and PlnD. In the present work, we show that the five PlnA-responsive operons are differentially expressed with regard to both timing and strength, and that the pheromone triggers a strong autoactivating loop of the regulatory unit (plnABCD) during an early stage of induction that gradually leads to enhanced activation of the other operons. The transport operon (plnGHSTUV), which is involved in the secretion of the pheromone and bacteriocins, is also expressed relatively early upon induction, but is quickly turned off soon after peak expression. Further investigation of the various promoters revealed that, although subtle differences within the promoter regions could account for the observed differential regulation, the presence of a downstream promoter-proximal sequence in one promoter was found to cause delayed peak activity. How phosphorylation regulates the activity of the pln response regulators was also accessed by direct mutagenesis at their phosphorylation sites. It was found that the two response regulators exert activity at two different levels: a low level when they are not phosphorylated and an elevated level when they are phosphorylated. The present data demonstrate that bacteriocin production in L. plantarum C11 is a highly regulated process, in which different regulatory mechanisms are applied to fine tune the timing and strength of expression of the five pln operons.

Amino Acid Sequence↗
PubMed2005

PSEUDO-RESPONSE REGULATOR 7 and 9 are partially redundant genes essential for the temperature responsiveness of the Arabidopsis circadian clock.

Environmental time cues, such as photocycles (light/dark) and thermocycles (warm/cold), synchronize (entrain) endogenous biological clocks to local time. Although much is known about entrainment of the Arabidopsis thaliana clock to photocycles, the determinants of thermoperception and entrainment to thermocycles are not known. The Arabidopsis PSEUDO-RESPONSE REGULATOR (PRR) genes, including the clock component TIMING OF CAB EXPRESSION 1/PRR1, are related to bacterial, fungal, and plant response regulators but lack the conserved Asp that is normally phosphorylated by an upstream sensory kinase. Here, we show that two PRR family members, PRR7 and PRR9, are partially redundant; single prr7-3 or prr9-1 mutants exhibit modest period lengthening, but the prr7-3 prr9-1 double mutant shows dramatic and more than additive period lengthening in the light and becomes arrhythmic in constant darkness. The prr7-3 prr9-1 mutant fails both to maintain an oscillation after entrainment to thermocycles and to reset its clock in response to cold pulses and thus represents an important mutant strongly affected in temperature entrainment in higher plants. We conclude that PRR7 and PRR9 are critical components of a temperature-sensitive circadian system. PRR7 and PRR9 could function in temperature and light input pathways or they could represent elements of an oscillator necessary for the clock to respond to temperature signals.

Alleles↗
PubMed2000

Acetyl phosphate-dependent activation of a mutant PhoP response regulator that functions independently of its cognate sensor kinase.

The two-component system is a signal communication network generally consisting of a sensor kinase that receives inputs from the environment and modifies the phosphorylated state of a response regulator that executes an adaptive behavior. PhoP is a response regulator that controls virulence gene expression in Salmonella enterica. Transcription of PhoP-regulated genes is modulated by the Mg(2+) levels detected by the sensor PhoQ. Here, we describe a PhoP mutant protein, PhoP*, that functions in the absence of its cognate sensor, thereby allowing transcription of PhoP-activated genes independently of the Mg(2+ )concentration in the environment. The PhoP* protein harbors a S93N substitution in the response regulator receiver domain. PhoP*-mediated transcription is abolished by either mutation of the aspartate residue that is conserved among response regulators as the site of phosphorylation or inactivation of the pta-encoded phosphotransacetylase. This enzyme mediates the production of acetyl phosphate, which has been shown to serve as a low molecular mass phosphate donor for certain response regulators. The purified PhoP* protein autophosphorylated from acetyl phosphate more efficiently than the wild-type PhoP protein in vitro. The PhoP* protein retained the capacity to interact with the PhoQ protein, which promoted phosphorylation of the PhoP* protein in vitro and abolished PhoP*-mediated transcription under high Mg(2+ )concentrations in vivo. Cumulatively, our results uncover a role of PhoQ in transcriptional repression during growth in millimolar Mg(2+ )and define a mutant response regulator form with an increased capacity to be phosphorylated by acetyl phosphate.

Alleles↗
PubMed2006

The DNA-binding domain of the Escherichia coli CpxR two-component response regulator is constitutively active and cannot be fully attenuated by fused adjacent heterologous regulatory domains.

Two-component systems (TCS) based on a sensor histidine kinase and a phosphorylated cognate target regulator allow rapid responses to environmental changes. TCS are highly evolutionarily conserved, though in only a few cases are the inducing signals understood. This study focuses on the Escherichia coli CpxR response regulator that responds to periplasmic and outer-membrane stress. N-terminal deletion mutations have been isolated that render the transcription factor constitutively active, indicating that the N terminus functions, in part, to keep the C-terminal winged-helix DNA-binding effector domain in an inactive state. Analysis of truncations spanning the CpxR interdomain region revealed that mutants retaining the alpha5 helix significantly augment activation. Hybrid proteins obtained by fusing the CpxR effector domain to structurally similar heterologous N-terminal regulatory domains, or even GFP, failed to restore repression to the C-terminal domain. These findings shed light on the mechanism of CpxR effector domain activation and on the investigation of constitutive mutants obtained by truncation in other TCS.

Bacterial Proteins↗
PubMed1992

Phosphorylation of bacterial response regulator proteins by low molecular weight phospho-donors.

Bacterial motility and gene expression are controlled by a family of phosphorylated response regulators whose activities are modulated by an associated family of protein-histidine kinases. In chemotaxis there are two response regulators, CheY and CheB, that receive phosphoryl groups from the histidine kinase, CheA. Here we show that the response regulators catalyze their own phosphorylation in that both CheY and CheB can be phosphorylated in the complete absence of any auxiliary protein. Both CheY and CheB use the N-phosphoryl group in phosphoramidate (NH2PO3(2-)) as a phospho-donor. This enzymatic activity probably reflects the general ability of response regulators to accept phosphoryl groups from phosphohistidines in their associated kinases. It provides a general method for the study of activated response regulators in the absence of kinase proteins. CheY can also use intermediary metabolites such as acetyl phosphate and carbamoyl phosphate as phospho-donors. These reactions may provide a mechanism to modulate cell behavior in response to altered metabolic states.

Aspartic Acid↗
PubMed2000

Arabidopsis ARR1 and ARR2 response regulators operate as transcriptional activators.

The genes coding for the response regulators ARR1 and ARR2 have previously been identified by in silico screening of an expression sequence tag database and subsequent cloning from both Arabidopsis cDNA and genomic libraries. Their structures, in which the N-terminal signal receiver domain is followed by the output domain, are characteristic of typical bacterial response regulators of the two-component regulatory systems that control responses to a variety of environmental stimuli. Here we present evidence that these response regulators actually work as transcription factors. ARR1 and ARR2 were localized in the nuclei of plant cells regardless of the presence or absence of their signal receiver domain. Their middle segments, which faintly resemble the mammalian oncogene product Myb, were capable of binding double-stranded DNA in a sequence-specific manner in vitro. Their C-terminal halves functioned as transactivation domains in plant cells when combined with the DNA-binding domain of yeast GAL4. They thus possess all the essential components of a transcriptional activator. Both ARR1 and ARR2 promoted expression of a reporter gene in plant cells through their own target sequence. Truncation of their N-terminal signal receiver domain led to an increase in transactivation. An as yet unidentified phospho-relay signal may modulate the capability for transactivation and/or DNA binding through the signal receiver domain.

Arabidopsis↗
PubMed1999

Phosphorylated aspartate in the structure of a response regulator protein.

Phosphorylation of aspartic acid residues is the hallmark of two- component signal transduction systems that orchestrate the adaptive responses of micro-organisms to changes in their surroundings. Two-component systems consist of a sensor kinase that interprets environmental signals and a response regulator that activates the appropriate physiological response. Although structures of response regulators are known, little is understood about their activated phosphorylated forms, due to the intrinsic instability of the acid phosphate linkage. Here, we report the phosphorylated structure of the receiver/phosphoacceptor domain of Spo0A, the master regulator of sporulation, from Bacillus stearothermophilus. The phosphoryl group is covalently bonded to the invariant aspartate 55, and co-ordinated to a nearby divalent metal cation, with both species fulfilling their electrostatic potential through interactions with solvent water molecules, the protein main chain, and with side-chains of amino acid residues strongly conserved across the response regulator family. This is the first direct visualisation of a phosphoryl group covalently linked to an aspartic acid residue in any protein, with implications for signalling within the response regulator family.

Adaptation, Biological↗
PubMed2003

Investigation of the role of electrostatic charge in activation of the Escherichia coli response regulator CheY.

In a two-component regulatory system, an important means of signal transduction in microorganisms, a sensor kinase phosphorylates a response regulator protein on an aspartyl residue, resulting in activation. The active site of the response regulator is highly charged (containing a lysine, the phosphorylatable aspartate, two additional aspartates involved in metal binding, and an Mg(2+) ion), and introduction of the dianionic phosphoryl group results in the repositioning of charged moieties. Furthermore, substitution of one of the Mg(2+)-coordinating aspartates with lysine or arginine in the Escherichia coli chemotaxis response regulator CheY results in phosphorylation-independent activation. In order to examine the consequences of altered charge distribution for response regulator activity and to identify possible additional amino acid substitutions that result in phosphorylation-independent activation, we made 61 CheY mutants in which residues close to the site of phosphorylation (Asp57) were replaced by various charged amino acids. Most substitutions (47 of 61) resulted in the complete loss of CheY activity, as measured by the inability to support clockwise flagellar rotation. However, 10 substitutions, all introducing a new positive charge, resulted in the loss of chemotaxis but in the retention of some clockwise flagellar rotation. Of the mutants in this set, only the previously identified CheY13DK and CheY13DR mutants displayed clockwise activity in the absence of the CheA sensor kinase. The absence of negatively charged substitution mutants with residual activity suggests that the introduction of additional negative charges into the active site is particularly deleterious for CheY function. Finally, the spatial distribution of positions at which amino acid substitutions are functionally tolerated or not tolerated is consistent with the presently accepted mechanism of response regulator activation and further suggests a possible role for Met17 in signal transduction by CheY.

Amino Acid Substitution↗
PubMed1998

A source of response regulator autophosphatase activity: the critical role of a residue adjacent to the Spo0F autophosphorylation active site.

Two-component signaling systems are used by bacteria, plants, and lower eukaryotes to adapt to environmental changes. The first component, a protein kinase, responds to a signal by phosphorylating the second component; a response regulator protein that often acts by inducing the expression of specific genes. Response regulators also have an autophosphatase activity that ensures that the proteins are not permanently activated by phosphorylation. The magnitude of this activity varies by at least 1000-fold between various response regulators, and the molecular features responsible for this varied autophosphatase activity have not been clearly defined. Using wild-type and mutant derivatives of the sporulation response regulator Spo0F, it has been demonstrated that a key residue in determining the magnitude of this activity is that at position 56 of Spo0F approximately P; this residue is adjacent to the site of phosphorylation, Asp 54. For example, Spo0F approximately P K56N has a 23-fold greater autophosphatase activity (t1/2 = 8 min) than wild-type Spo0F approximately P (t1/2 = 180 min). It is suggested that, by analogy to the GTPase activity of p21(ras) and by examining the crystallographic structure of Spo0F, that the carboxyamide of the mutant Asn 56 may favorably position a catalytic water near the protein acyl phosphate to promote Spo0F approximately P K56N hydrolysis. It is also deduced that Lys 56 in the wild-type protein is critical for the efficient interaction and phosphoryl transfer between Spo0F and it's cognate protein kinase, KinA. Comparison of the known response regulators shows that inefficient autophosphatases (t1/2 on the order of hours) typically contain an amino acid residue with a long side chain at the position equivalent to 56 in Spo0F, whereas efficient autophosphatases (t1/2 on the order of minutes) frequently contain a residue with a carboxyamide or carboxylate side chain at this position. It appears that, by altering residues adjacent to the active site, the autophosphatase activity of response regulator proteins has been attenuated to match the diverse biological roles played by these proteins.

Adenosine Triphosphate↗
PubMed1995

Mechanism of activation of a response regulator: interaction of NtrC-P dimers induces ATPase activity.

NtrC is the transcriptional activator for nitrogen-regulated promoters and, as a response regulator, belongs to the protein family of two-component systems. The activity of all response regulators is modulated by phosphorylation of the conserved N-terminal receiver domain. Phosphorylation of the dimeric NtrC has two consequences: (i) a strong increase in the cooperative binding of NtrC to two adjacent binding sites and (ii) activation of NtrC as an ATPase. Here we show that phosphorylation of NtrC is not sufficient for activation of NtrC. At low protein concentrations (50 nM), phosphorylated NtrC was only active as an ATPase upon cooperative binding to DNA. At high protein concentrations (above 50 nM), NtrC was active in the absence of DNA, and activation occurred in parallel with the formation of high-molecular-weight aggregates. We infer that activation of NtrC involves an interaction between two NtrC-P dimers and proceeds in two steps. The first step is the phosphorylation of NtrC. The second step is the interaction between two NtrC-P dimers. This interaction induces the conformational change in NtrC-P to the active conformation.

Adenosine Triphosphatases↗
PubMed1996

The predicted amino acid sequence of the Salmonella typhimurium virulence gene mviAA(+) strongly indicates that MviA is a regulator protein of a previously unknown S. typhimurium response regulator family.

The Salmonella typhimurium virulence gene mviA+ has a predicted amino acid sequence with homology to the N-terminal 112-amino-acid sequence of response regulator proteins. A previously described mutant allele (mviA), which restores virulence to avirulent LT2 strains, was shown to contain a point mutation which would be predicted to cause a single amino acid change, V-102-->G (W. H. Benjamin, Jr., J. Yother, P. Hall, and D. E. Briles, J. Exp. Med. 1,74:1073-1083, 1991). A comparison of the nucleotide sequence of mviA+ with that of the Escherichia coli and Salmonella typhi genes revealed a high degree of conservation.

Alleles↗