Gene/Protein Disease Symptom Drug Enzyme Compound
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In addition to Ipa proteins and IcsA, which are involved in entry into epithelial cells and intercellular spread, respectively, Shigella secretes a 110 kDa protein, designated SepA. We report the identification, cloning, and nucleotide sequence determination of the sepA gene, analysis of SepA secretion, and construction and characterization of a sepA mutant. The sepA gene is carried by the virulence plasmid and codes for a 150 kDa precursor. Upon secretion, which does not involve accessory proteins encoded by the virulence plasmid, the precursor is converted to a mature protein of 110 kDa by two cleavages removing an N-terminal signal sequence and a C-terminal fragment. Extensive similarities were detected between the sequence of the first 500 residues of mature SepA and the N-terminal region of IgA1 proteases from Neisseria gonorrhoeae and Haemophilus influenzae, the Tsh haemagglutinin of an avian pathogenic Escherichia coli, and the Hap protein involved in adhesion and penetration of H. influenzae. The C-terminal domain of the SepA precursor, which is not present in the secreted protein, exhibits sequence similarity with pertactin of Bordetella pertussis and the ring-forming protein of Helicobacter mustelae. Construction and phenotypic characterization of a sepA mutant indicated that SepA is required neither for entry into cultured epithelial cells nor for intercellular dissemination. However, in the rabbit ligated ileal loop model, the sepA mutant exhibited an attenuated virulence, which suggests that SepA might play a role in tissue invasion.
Mol Microbiol 1995 Jul
PMID:SepA, the major extracellular protein of Shigella flexneri: autonomous secretion and involvement in tissue invasion. 747 98

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

The clinical manifestations of cholera are largely attributable to the actions of a secreted hexameric AB5 enterotoxin (choleragen). We have independently solved and refined the three-dimensional structure of choleragen at 2.5 A resolution. The structure of the crystalline toxin closely resembles that described for the heat-labile enterotoxin from Escherichia coli (LT) with which it shares 80% sequence homology. In both cases, the wedge-shaped A subunit is loosely held high above the plane of the pentameric B subunits by the tethering A2 chain. The most striking difference between the two toxins occurs at the carboxyl terminus of the A2 chain. Whereas the last 14 residues of the A2 chain of LT threading through the central pore of the B5 assembly form an extended chain with a terminal loop, the A2 chain of choleragen remains a nearly continuous alpha-helix throughout its length. The four carboxyl-terminal residues of the A2 chain (KDEL sequence), disordered in the crystal structure of LT, are clearly visible in choleragen's electron-density map. In the accompanying article we describe the three-dimensional structure of the isolated B pentamer of cholera toxin (choleragenoid). Comparison of the crystalline coordinates of choleragen, choleragenoid, and LT provides a solid three-dimensional foundation for further experimental investigation. These structures, along with those of related toxins from Shigella dysenteria and Bordetella pertussis, offer a first step towards the rational design of new vaccines and anti-microbial agents.
J Mol Biol 1995 Aug 25
PMID:The three-dimensional crystal structure of cholera toxin. 765 73

We have carried out a functional analysis of invl and invJ, two Salmonella typhimurium genes required for this organism to gain access to cultured mammalian cells. These genes are located immediately down-stream of invC, a previously identified gene also required for bacterial invasion. Non-polar mutations in either of these genes rendered S. typhimurium severely defective for entry into cultured epithelial cells, although these mutations did not affect the ability of these organisms to attach to those cells. Nucleotide sequence analysis revealed that the invl and invJ genes encode proteins with molecular weights of 18,077 and 36,415, respectively. Polypeptides of similar sizes were observed when these genes were expressed in a bacteriophage T7 RNA polymerase-based expression system. Comparison of the predicted sequences of invl and invJ with translated sequences in the existing databases indicated that these proteins are identical to the previously identified S. typhimurium SpaM and SpaN proteins. Further analysis of these sequences revealed regions of homology between Invl and the N-terminus of IpaB of Shigella spp. and between InvJ and EaeB of enteropathogenic Escherichia coli. Localization studies by immunoblot analysis indicated that InvJ is secreted to the culture supernatant, a surprising finding since this protein also lacks a typical signal sequence. Mutations in invG and invC, two members of the Salmonella inv locus, effectively prevented the transport of InvJ to the culture supernatant. Thus, InvJ is the first identified target of the protein secretion apparatus encoded in the inv locus and therefore a candidate to have effector functions related to bacterial entry.
Mol Microbiol 1995 Jan
PMID:Functional analysis of the Salmonella typhimurium invasion genes invl and invJ and identification of a target of the protein secretion apparatus encoded in the inv locus. 775 94

6' gentamicin acetyltransferases detoxify aminoglycoside antibiotics containing a 6' amino group. We tested whether a 6' gentamicin acetyltransferase gene (6' gat) of Shigella sp. is suitable as selectable gene in plant transformation using kanamycin (Km) as a substrate. A comparative transformation experiment using Nicotiana tabacum SR1 protoplasts showed that 6' gat is as effective for selection of transformants as the commonly used neomycin phosphotransferase II (nptII). In stably transformed plants we detected moderate levels of the 6' gat mRNA. An enzymatic assay was developed with which the acetyltransferase activity of the protein is easily demonstrated.
Plant Mol Biol 1994 Dec
PMID:A 6' gentamicin acetyltransferase gene allows effective selection of tobacco transformants using kanamycin as a substrate. 785 36

We have used the polymerase chain reaction (PCR) to detect shigellae, EIEC and ETEC in stool specimens of diarrhoeic patients returning from tropical countries. As compared to culture (7.1% positive specimens), which recognizes only Shigella strains, PCR performed on bacterial growth from directly inoculated MacConkey agar plates and directed against virulence-associated genes present in both Shigella and EIEC was positive in 19.8% of the samples. We assumed that these additional positive results represent true rather than false positive samples because identical results for each single specimen were obtained using two different PCR systems and because positive results (culture as well as PCR) were exclusively found in patients with recent travel but not in those who acquired diarrhoea in a developed country where these organisms are not endemic. PCR detecting LT- and ST-specific sequences was positive in 18.5% of the patients with recent travel. Again no positive cases were identified in controls. Combining PCR and culture results, at least one bacterial pathogen was found in more than 50% of the patients with recent travel. We conclude that PCR is superior to culture methods for the detection of Shigella, EIEC and ETEC in travel-associated diarrhoea.
Mol Cell Probes 1994 Aug
PMID:Detection of shigellae, enteroinvasive and enterotoxigenic Escherichia coli using the polymerase chain reaction (PCR) in patients returning from tropical countries. 787 70

The authors analyze current data on genetic control of the principal factors of pathogenicity of Shigella, Salmonella, Yersinia, Listeria and Proteus. They review the phases in the development of an infectious process and discuss problems in interaction of chromosomal and plasmid genes determining the pathogenicity of the said bacteria.
Mol Gen Mikrobiol Virusol
PMID:[The role of the chromosome and its interaction with extrachromosomal determinants during the process of genetic control of bacterial pathogenicity]. 789 31

The SEF14 gene cluster of Salmonella enteritidis was recently shown to contain three genes, sefABC, encoding a unique fimbrin, and proteins homologous to fimbrial chaperones and outer membrane proteins (ushers), respectively. A fourth open reading frame, designated sefD, was found immediately downstream of sefABC and overlapping sefC. The translated protein sequence of sefD was unique, but the composition was similar to that of other bacterial fimbriae. SefD was produced in abundance by wild-type S. enteritidis as shown by Western blot analysis using antibodies raised to affinity-purified, recombinant SefD. Furthermore, unusually long, thin, fimbriae-like structures were evident on S. enteritidis and Escherichia coli by immunoelectron microscopy, but in other bacterial species SefD was expressed as amorphous material. Therefore, in S. enteritidis and E. coli, SefD is the predominant structural subunit of SEF18. The SEF18 fimbriae-like structures were shown to be serologically distinct from the three known S. enteritidis fimbriae SEF14, SEF17 and SEF21. Furthermore, SEF18 was still produced in sefA insertion mutants, indicating that SEF14 and SEF18 were structurally distinct. Thus, the SEF14 gene cluster is the first example in the Enterobacteriaceae of a gene cluster that encodes two fimbrin-like proteins, which are assembled into two distinct cell-surface structures, SEF14 and SEF18. DNA hybridization and Western blot analyses showed that SefD was widely distributed among the Enterobacteriaceae and was present in E. coli, Shigella, Enterobacter, Citrobacter, Erwinia, Hafnia, Klebsiella, Providencia, and Proteus but not in the non-Enterobacteriaceae Gram-negative bacteria Pseudomonas and Aeromonas, or in Gram-positive bacteria Bacillus or Staphylococcus.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Microbiol 1994 Jun
PMID:Unique fimbriae-like structures encoded by sefD of the SEF14 fimbrial gene cluster of Salmonella enteritidis. 793 97

The Gram-positive bacterium Listeria monocytogenes is a facultative intracellular parasite that invades and multiplies within diverse eukaryotic cell types. An essential pathogenicity determinant is its ability to move in the host cell cytoplasm and to spread within tissues by directly passing from one cell to another. The propulsive force for intracellular movement is thought to be generated by continuous actin assembly at the rear end of the bacterium. Moving bacteria that reach the plasma membrane induce the formation of long membranous protrusions that are internalized by neighbouring cells, thus mediating the spread of infection. The unrelated pathogens Shigella and Rickettsia use a similar process of actin-based motility to disseminate in infected tissues. This review focuses on the bacterial and cellular factors involved in the actin-based motility of L. monocytogenes.
Mol Microbiol 1994 Aug
PMID:The actin-based motility of the facultative intracellular pathogen Listeria monocytogenes. 799 57

Flagellin genes (fliC) were detected in two species of the genus Shigella. The fliCSF gene cloned from Shigella flexneri produced normal-type flagella in an Escherichia coli delta fliC strain while the fliCSS genes from two Shigella sonnei strains produced curly-type flagella and their expression is repressible by Salmonella FljA repressor. The fliCSF gene (1650 bp) shared high similarity with the E. coli fliCE gene not only in the 5' and 3' constant sequences but also in the upstream and downstream sequences. The fliCSS genes (1572 bp) shared high similarity with the Salmonella typhimurium fliCS gene in the operator and 3' constant sequences and also shared high similarity with the fliCE gene in the downstream sequence, suggesting that the fliCSS gene has undergone horizontal transfer and recombination. Differences in nucleotide sequences of the central variable regions among the four fliC genes, including fliCE and fliCS, suggest that they started differentiation in each lineage approximately 80 million years ago. Loss of motility in Shigella seems to be evolutionarily a recent event.
Mol Microbiol 1994 Apr
PMID:Molecular characterization of intact, but cryptic, flagellin genes in the genus Shigella. 805 52


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