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Query: UNIPROT:P06889 (Mol)
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The genes coding for the RNA-polymerase beta,beta'-subunits and adjacent ribosomal protein genes in Escherichia coli, Salmonella typhimurium, Shigella flexneri, Serratia marcescens, Proteus mirabilis and Pseudomonas putida are compared by the Southern hybridization procedure. In all the species studied close clustering of the genes rplKAJL and rpoBC is demonstrated. Preliminary physical maps for these genes in S. typhimurium, S. flexneri, S. marcescens and P. mirabilis are proposed. Rifampicin is shown to stimulate the beta,beta'-subunit synthesis in all the species studied, suggesting the existence of attenuators localized in front of the rpoBC genes. The similar arrangement of the genes rplKAJLrpoBC in a number of bacterial species is proposed to be due to common mechanisms of their coordinate expression.
Mol Biol (Mosk)
PMID:[Similar organization of beta,beta'-subunit RNA-polymerase genes and adjacent ribosomal protein genes in Enterobacteriaceae and Pseudomonas putida]. 300 45

On the virulence plasmid of Shigella flexneri the virG region required for cell-to-cell spread of the bacterium encodes a 130 kiloDalton (kD) antigen and Region-2 essential for the bacterial invasion of epithelial cells encodes 57, 43 and 39 kD antigens. The expression of these four antigens is positively regulated by the 30 kD protein encoded by virF, whose nucleotide sequence had been determined and which was previously found to be essential for virulence. An approximately 3.8 kilobase (kb) RNA transcript is found to be transcribed by the virG region and is positively regulated by the virF protein resulting in increased production of the 130 kD antigen. The virF sequence is conserved among all shigellae and enteroinvasive Escherichia coli.
Mol Microbiol 1988 Sep
PMID:Expression of four virulence antigens of Shigella flexneri is positively regulated at the transcriptional level by the 30 kiloDalton virF protein. 314 42

Different compounds derived from choline, and obtained by demethylation or by oxidation of the primary alcohol group with subsequent N-demethylation, were tested as inducer agents of acid phosphatase and cholinesterase in Ps. aeruginosa. It was found that betaine and dimethylglycine were the most effective inducers of both enzyme activities. These metabolites including choline itself, were not inducers of acid phosphatase and cholinesterase in other Gram-negative bacteria such as: Escherichia coli, Salmonella typhimurium, Shigella flexneri, Enterobacter liquefacciens and Proteus mirabilis. The acid phosphatase activities found in these bacteria were not inhibited in vitro by choline, betaine and phosphorylcholine. From these results it may be concluded that the acid phosphatase activity from Ps. aeruginosa is different from the same activity observed in the other bacteria. In addition, it is also shown that Ps. aeruginosa acid phosphatase and cholinesterase were inhibited by a number of compounds containing a positively charged amino group, with methyl or ethyl groups bound to it. These results seem to confirm that Ps. aeruginosa acid phosphatase and cholinesterase may contain a similar anionic site.
Mol Cell Biochem 1984 Sep
PMID:Pseudomonas aeruginosa acid phosphatase and cholinesterase induced by choline and its metabolic derivatives may contain a similar anionic peripheral site. 643 82

Previously, the PhoP-repressed locus prgH was identified as important for signalling epithelial cells to endocytose Salmonella typhimurium. Characterization of prgH revealed that it is an operon of four genes encoding polypeptides of 392 (prgH), 80 (prgI), 101 (prgJ) and 252 amino acid residues (prgK). Synthesis of the 2.6 kb prgHIJK transcript was repressed in bacteria that activate PhoP/PhoQ, indicating that PhoP/PhoQ regulates prgHIJK by transcriptional repression. The prgI, prgJ and prgK predicted gene products were similar to Shigella flexneri and Yersinia enterocolitica proteins required for secretion of Ipa and Yop virulence factors. Analysis of the culture supernatants from wild-type S. typhimurium demonstrated that at least 25 polypeptides larger than 14 kDa could be detected. In contrast, prgH1::TnphoA, phoP-constitutive and hil-deletion mutants had significant defects in their supernatant protein profiles. The invasion and supernatant protein profile defects of the prgH1::TnphoA mutant were both complemented by a 5.1 kb plasmid that included prgHIJK. These results suggest that PhoP/PhoQ regulates extracellular transport of proteins by transcriptional repression of secretion determinants and that secreted proteins may be involved in signalling epithelial cells to endocytose bacteria.
Mol Microbiol 1995 Jul
PMID:PhoP/PhoQ transcriptional repression of Salmonella typhimurium invasion genes: evidence for a role in protein secretion. 747 3

Data on the genetic basis of the classification of Shigella flexneri serological variants 1-5 are presented. Subserovars "a" are related to monolysogenic variants of the basic lipopolysaccharide (LPS) structure 0 antigen 3,4, "b" to bilysogenic ones. A scheme of their antigenic variability, with regard to loss of one or both prophages is presented. This scheme helps differentiate between antigenic variability and mixed or superinfections. Recent reports confirming our previously published suggestion to exclude serovar 6 (Shigella newcastle) from Shigella flexneri are analyzed. We propose that antigenic variability of S. flexneri 1-5 results from lysogenization of naturally occurring strains. The possibility of consecutive lysogenization of S. flexneri y (-:3,4) by bacteriophages 6 and 7 has been shown, as exemplified by the circulation of a previously unknown subserovar IV:7,8.
Mol Gen Mikrobiol Virusol
PMID:Antigenic variability of Shigella flexneri serovars 1-5. 747 27

A novel virulence gene (virA) was identified upstream of the virG gene on the large plasmid of Shigella flexneri 2a YSH6000. Characterization of virA mutants infecting MK2 epithelial cell monolayers revealed that their invasive capacity was decreased to less than one fifth of the wild-type level. Nevertheless, the bacteria were capable of expressing and secreting IpaB, IpaC and IpaD proteins. The virA mutants were also impaired in their ability to spread intercellularly, since the bacteria gave rise to a small number of foci in a focus-plaque-forming test with MK2 cells. Although virG expression was slightly decreased in the virA mutants, introduction of a cloned virG gene into a virA mutant, N1945, failed to restore spreading ability. Although, introduction of a cloned virA gene into N1945 restored invasiveness and spreading ability, the reduced virG transcription level was not affected, indicating that the reduced virG expression in virA mutants does not play a major role in defective intercellular spreading. The nucleotide sequence of the virA region revealed that the virA gene was located 528 bp upstream of the virG gene, in the opposite orientation. The deduced amino acid sequence of the VirA protein indicated a 44.7 kDa protein with no homology to known proteins. The VirA protein was secreted into the culture supernatant, a process that required the Mxi and Spa loci. The expression of virA was under the control of the virB gene, the positive regulator of the ipa, mxi and spa operons. These results indicate that virA is a new member of the invasion regulon directed by virB and that the VirA function is involved in invasion and intercellular spreading.
Mol Microbiol 1995 Jul
PMID:Identification of a novel virulence gene, virA, on the large plasmid of Shigella, involved in invasion and intercellular spreading. 749 73

The O antigen of the Shigella flexneri lipopolysaccharide (LPS) is an important virulence determinant and immunogen. We have isolated S. flexneri mutants which produce a semi-rough LPS by using an O-antigen-specific phage, Sf6c. Western immunoblotting was used to show that the LPS produced by the semi-rough mutants contained only one O-antigen repeat unit. Thus, the mutants are deficient in production of the O-antigen polymerase and were termed rfc mutants. Complementation experiments were used to locate the rfc adjacent to the rfb genes on plasmid clones previously isolated and containing this region (D. F. Macpherson, R. Morona, D. W. Beger, K.-C. Cheah, and P. A. Manning, Mol. Microbiol 5:1491-1499, 1991). A combination of deletions and subcloning analysis located the rfc gene as spanning a 2-kb region. Insertion of a kanamycin resistance cartridge into a SalI site in this region inactivated the rfc gene. The DNA sequence of the rfc region was determined. An open reading frame spanning the SalI site was identified and encodes a protein with a predicted molecular mass of 43.7 kDa. The predicted protein is highly hydrophobic and showed little sequence homology with any other protein. Comparison of its hydropathy plot with that of other Rfc proteins from Salmonella enterica (typhimurium) and Salmonella enterica (muenchen) revealed that the profiles were similar and that the proteins have 12 or more potential membrane-spanning segments. A comparison of the S. flexneri rfc gene and protein product with other rfc and rfc-like proteins revealed that they have a similarly low percentage of G + C content and have similar codon usage, and all have a high percentage of rare codons. An attempt to identify the S. flexneri Rfc protein was unsuccessful, although proteins encoded upstream and downstream of the rfc gene could be identified. Examination of the distribution of rare or minor codons in the rfc gene revealed that it has several minor codons within the first 25 amino acids. This is in contrast to the upstream gene rfbG, which also has a high percentage of rare codons but whose gene product could be detected. The positioning of the rare codons in the rfc gene may restrict translation and suggests that minor isoaccepting tRNA species may be involved in translational regulation of rfc expression. The low percentage of G + C content of rfc genes may be a consequence of the selection pressure to maintain this form of control.
 ...
PMID:Characterization of the rfc region of Shigella flexneri. 750 20

The rfb region of Shigella flexneri encodes the proteins required to synthesize the O-antigen component of its cell surface lipopolysaccharides (LPS). We have previously reported that a region adjacent to rfb was involved in regulating the length distribution of the O-antigen polysaccharide chains (D. F. Macpherson et al., Mol. Microbiol. 5:1491-1499, 1991). The gene responsible has been identified in Escherichia coli O75 (called rol [R. A. Batchelor et al., J. Bacteriol. 173:5699-5704, 1991]) and in E. coli O111 and Salmonella enterica serovar typhimurium strain LT2 (called cld [D. A. Bastin et al., Mol. Microbiol. 5:2223-2231, 1991]). Through a combination of subcloning, deletion, and transposon insertion analysis, we have identified a gene adjacent to the S. flexneri rfb region which encodes a protein of 36 kDa responsible for the length distribution of O-antigen chains in LPS as seen on silver-stained sodium dodecyl sulfate-polyacrylamide gels. DNA sequence analysis identified an open reading frame (ORF) corresponding to the rol gene. The corresponding protein was almost identical in sequence to the Rol protein of E. coli O75 and was highly homologous to the functionally identical Cld proteins of E. coli O111 and S. enterica serovar typhimurium LT2. These proteins, together with ORF o349 adjacent to rfe, had almost identical hydropathy plots which predict membrane-spanning segments at the amino- and carboxy-terminal ends and a hydrophilic central region. We isolated a number of TnphoA insertions which inactivated the rol gene, and the fusion end points were determined. The PhoA+ Rol::PhoA fusion proteins had PhoA fused within the large hydrophilic central domain of Rol. These proteins were located in the whole-membrane fraction, and extraction with Triton X-100 indicated a cytoplasmic membrane location. This finding was supported by sucrose density gradient fractionation of the whole-cell membranes and of E. coli maxicells expressing L-[35S]methionine-labelled Rol protein. Hence, we interpret these data to indicate that the Rol protein is anchored into the cytoplasmic membrane via its amino- and carboxy-terminal ends but that the majority of the protein is located in the periplasmic space. To confirm that rol is responsible for the effects on O-antigen chain length observed with the cloned rfb genes in E. coli K-12, it was mutated in S. flexneri by insertion of a kanamycin resistance cartridge. The resulting strains produced LPS with O antigens of nonmodal chain length, thereby confirming the function of the rol gene product. We propose a model for the function of Rol protein in which it acts as a type of molecular chaperone to facilitate the interaction of the O-antigen ligase (RfaL) with the O-antigen polymerase (Rfc) and polymerized, acyl carrier lipid-linked, O-antigen chains. Analysis of the DNA sequence of the region identified a number of ORFs corresponding to the well-known gnd and hisIE genes. The rol gene was located immediately downstream of two ORFs with sequence similarity to the gene encoding UDPglucose dehydrogenase (HasB) of Streptococcus pyogenes. The ORFs arise because of a deletion or frameshift mutation within the gene we have termed udg (for UDPglucose dehydrogenase).
 ...
PMID:Molecular, genetic, and topological characterization of O-antigen chain length regulation in Shigella flexneri. 753 68

Genes required for entry of Shigella flexneri into epithelial cells in vitro are clustered in two adjacent loci, one of which encodes secretory proteins, the IpaA-D proteins, and the other their dedicated secretion apparatus, the Mxi-Spa translocon. Ipa secretion, which is induced upon contact of bacteria with epithelial cells, is prevented during growth in vitro. Here, we show that ipaB and ipaD mutations lead to enhanced secretion of a set of about 15 proteins. These extracellular proteins and some Ipas associate in organized structures consisting of extended sheets. Growth of the wild-type strain in the presence of Congo red is shown to induce protein secretion through the Mxi-Spa translocon. Cultures grown to stationary phase in the presence of Congo red contain extracellular filaments whose composition and morphology are similar to those produced by the hypersecreting ipaB and ipaD mutants.
Mol Microbiol 1995 Apr
PMID:Enhanced secretion through the Shigella flexneri Mxi-Spa translocon leads to assembly of extracellular proteins into macromolecular structures. 756 91

Pseudomonas syringae pv. syringae 61 contains a 25-kb hrp cluster that is sufficient to elicit the hypersensitive response (HR) in nonhost plants. Previous studies have shown that mutations in complementation groups VIII, IX, and XI in the hrp cluster abolished the ability of the bacterium to cause the HR. The sequence of a 3.7-kb SmaI-SstI fragment covering groups VIII and IX now reveals five open reading frames (ORFs) in the same transcript, designated as hrpU, hrpW, hrpO, hrpX, and hrpY, and predicted to encode proteins of 14,795, 23,211, 9,381, 28,489, and 39,957 Da, respectively. The hrpU, hrpW, hrpO, hrpX, and hrpY genes are homologous and arranged colinearly with the yscQ/spa33/spaO, yscR/spa24/spaP, yscS/spa9/spaQ, yscT/spa29/spaR, and yscU/spa40/spaS genes of Yersinia spp., Shigella flexneri, and Salmonella typhimurium, respectively. These proteins also show similarity to Fli/Flh proteins of Bacillus and enteric bacteria. The Ysc and Spa proteins are involved in the secretion of virulence factors, like the Yop and Ipa proteins. Fli/Flh proteins are involved in flagellar biogenesis. The sequence of a 2.9-kb EcoRV-EcoRI DNA fragment containing mainly group XI revealed five ORFs, designated hrpC, hrpD, hrpE, hrpF, and hrpG, predicted to encode proteins of 29,096, 15,184, 21,525, 7,959, and 13,919 Da, respectively. The first three genes belong to an operon containing hrpZ, which encodes an extracellular protein that elicits the HR. hrpF and hrpG are two potential ORFs upstream of hrpH in the hrpH operon. HrpC is homologous to Yersinia YscJ, Pseudomonas solanacearum HrpI, Xanthomonas compestris pv. vesicatoria HrpB3, and Rhizobium fredii NolT. HrpE is similar to YscL of Yersinia spp. P. s. pv. syringae 61 Hrp proteins are most similar to Ysc proteins among those homologs. TnphoA insertions in hrpC, hrpE, hrpW, hrpX, and hrpY abolished the ability of P. s.pv. syringae 61 to secrete HrpZ (harpinPss), as determined by immunoblot analysis of cell-bound and culture supernatant fractions. Thus, many of the proteins required for flagellar biogenesis and virulence protein secretion in plant and animal pathogens may have a common ancestry.
Mol Plant Microbe Interact
PMID:The complete hrp gene cluster of Pseudomonas syringae pv. syringae 61 includes two blocks of genes required for harpinPss secretion that are arranged colinearly with Yersinia ysc homologs. 757 17


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