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)

Regulation of toxin production in the gram-positive anaerobe Clostridium perfringens occurs at the level of transcription and involves a two-component signal transduction system. The sensor histidine kinase is encoded by the virS gene, while its cognate response regulator is encoded by the virR gene. We have constructed a VirR expression plasmid in Escherichia coli and purified the resultant His-tagged VirR protein. Gel mobility shift assays demonstrated that VirR binds to the region upstream of the pfoA gene, which encodes perfringolysin O, but not to regions located upstream of the VirR-regulated plc, colA, and pfoR genes, which encode alpha-toxin, collagenase, and a putative pfoA regulator, respectively. The VirR binding site was shown by DNase I footprinting to be a 52-bp core sequence situated immediately upstream of the pfoA promoter. When this region was deleted, VirR was no longer able to bind to the pfoA promoter. The binding site was further localized to two imperfect direct repeats (CCCAGTTNTNCAC) by site-directed mutagenesis. Binding and protection analysis of these mutants indicated that VirR had the ability to bind independently to the two repeated sequences. Based on these observations it is postulated that the VirR positively regulates the synthesis of perfringolysin O by binding directly to a region located immediately upstream of the pfoA promoter and activating transcription.
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PMID:The VirR response regulator from Clostridium perfringens binds independently to two imperfect direct repeats located upstream of the pfoA promoter. 1061 63

It was demonstrated recently that three histidine kinases genes in Candida albicans contributed to virulence, indicating the importance of signaling pathways regulated by histidine kinases. In the present study, using a set of degenerate primers, RT-PCR was performed with cDNA of A. fumigatus as a template. PCR products were cloned and sequenced. After Blast analysis, it was found that one fragment (named as AFHK1), 305 bp, was highly homologous to the two-component histidine kinase tesA gene of Aspergillus nidulans. But AFHKI was not completely identical to the FOS-1 gene of A. fumigatus. The same A. fumigatus strain was used to inoculate the mice for a murine model of invasive pulmonary aspergillosis (IPA). After 5-days post-inoculation, the lungs of infected animals were removed and incubated for 2 h at 37 degrees C in digestion buffer containing collagenase and trypsin. The pulmonary cells were removed by passing the suspension through a sieve. The non-filterable hyphae were treated with deoxygenated sodium cholate. Total RNA of A. fumigatus isolated from the infected tissues or cultured in vitro was extracted. With AFHKI as a probe. a Northern blot was performed. A 3.0 kb (approximate) transcript of mRNA was detected corresponding to the putative histidine kinase gene. It was demonstrated that that gene was expressed at markedly higher levels in vivo than in vitro. The results suggest that this gene may contribute to the survival and virulence of A. fumigatus.
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PMID:Cloning of Aspergillus fumigatus histidine kinase gene fragment and its expression during invasive infection. 1191 67

Vibrio alginolyticus is an opportunistic pathogen in both humans and marine animals. Collagenase encoded by colA is considered to be one of the virulence factors. Expression of colA is regulated by multiple environmental factors, e.g., temperature, growth phase, and substrate. To elucidate the mechanism of regulation of colA expression, transposon mutagenesis was performed. VarS, a sensor histidine kinase of the two-component regulatory system, was demonstrated to regulate the expression of colA. VarA, a cognate response regulator of VarS, was also identified and shown to be involved in the regulation of colA expression. In vitro phosphorylation assays showed that phosphorylated VarS acted as a phosphoryl group donor to VarA. A site-directed mutagenesis study showed that the His300, Asp718 and His874 residues in VarS were essential for the phosphorylation of VarS, and the Asp54 residue in VarA was likely to receive the phosphoryl group from VarS. The results demonstrate that the VarS/VarA two-component regulatory system regulates the expression of collagenase in V. alginolyticus.
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PMID:Expression of Collagenase is Regulated by the VarS/VarA Two-Component Regulatory System in Vibrio alginolyticus. 2899 50

Mushrooms are potential sources of novel natural cosmeceutical ingredients. This study was conducted to evaluate the cosmetic (skincare) benefits of the valuable medicinal species Ophiocordyceps sinensis (=Cordyceps sinensis). The mycelial extracts of 2 O. sinensis strains, Cs-HK1 and Cs-4, prepared sequentially with ethyl acetate, ethanol, and hot water were tested with in vitro assays for tyrosinase-, collagenase-, and elastase-inhibitory activity. The ethyl acetate extracts of both fungal strains showed potent antityrosinase and antielastase activity, with low half-maximal inhibitory concentrations (0.14-0.47 mg/mL) comparable to those of the respective reference compounds (arbutin and epigallocatechin gallate). All mycelial extracts exhibited moderate or significant anticollagenase activity; most extracts showed a significant photoprotective effect with a sun protection factor up to 25. The results from this study show the potential use of O. sinensis as a source of cosmetic ingredients for skincare applications.
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PMID:Cosmetic and Skincare Benefits of Cultivated Mycelia from the Chinese Caterpillar Mushroom, Ophiocordyceps sinensis (Ascomycetes). 3005 54