Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To analyze the possible mechanisms by which coxsackie B1 virus infection affects the invasiveness of Shigella flexneri, we have studied the influence of intracellular levels of Na+ and K+, ATPase activity, cytoplasmic membrane potential, cAMP level and cell communication through gap junctions. 3h after adsorption of viable or UV-inactivated coxsackie B1 virus the Na(+)-K+ gradient of the cell collapsed, ATPase activity decreased, the cytoplasmic membranic potential-dependent tetraphosphonium ion uptake were reduced. No changes in cAMP or intercellular cell communication were observed. S. flexneri invasiveness in HEp-2 cell pretreated with viable or UV-inactivated coxsackie B 1 virus was enhanced, but bacterial invasiveness was unchanged in K(+)-depleted HEp-2 cells, cell cultures with high intracellular Na+ content or ouabain pre-treated cells compared to control cells. We found no correlation between the enhanced bacterial invasiveness in the early phase of coxsackie B 1 virus infection in HEp-2 cell cultures and intracellular K+ depletion, high intracellular Na+ content, inhibited Na(+)-K+ ATPase activity or membranic depolarization.
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PMID:Coxsackie B1 virus-induced changes in cell membrane-associated functions are not responsible for altered sensitivity to bacterial invasiveness. 131 9

The effect of interferon treatment on interaction of Shigella flexneri with in vitro cultured cells was investigated. Pretreatment of HEp-2 cells with human interferons had no effect on the susceptibility of cells to S. flexneri, measured by invasiveness and adhesiveness. Human leukocyte interferon and human recombinant interferon-alpha-A reduced adhesiveness, intracellular multiplication and invasiveness of S. flexneri in HEp-2 cells preinfected with coxsackie B1 virus. Also non-receptor mediated-phagocytosis was reduced by interferon treatment in virus infected cells. The interferon effects were dependent on continuous protein synthesis, because they were not expressed when cycloheximide or abrin was added to the virus infected cell cultures. No effect of interferon was detected on intracellular content of Na+ or K+, Na(+)-K+ activated ATPase activity or cytoplasma membrane polarity, in virus infected or control cell cultures. The interferon effect on bacterial invasiveness seems to be dependent on an interferon receptor interaction on cytoplasma membrane level because directly microinjected interferon showed no effect.
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PMID:Interferon treatment reduced adherence, invasiveness and intracellular multiplication of Shigella flexneri in coxsackie B1 virus-infected cells. 132 37

J774, a continuous macrophage cell-line, was infected by M90T, an invasive isolate of Shigella flexneri serotype 5 and BS176, its non invasive derivative--which does not harbor the 220 kbase virulence plasmid pWR100. Killing of host cells by intracellular M90T, commenced one hour after infection and was completed by 4 hours. Intracellular BS176 did not kill cells during the same period. Cell protein biosynthesis was totally inhibited by both strains within 2 hours of infection thus indicating that shiga-like toxin 1 (SLT1) could not account for early killing. On the other hand a sharp decrease in intracellular ATP was observed after 1 hour in cells infected with M90T. No significant increase in ATPase activity could be detected. A sharp increase in pyruvate production starting immediately after infection indicated impairement in mitochondrial respiration, which accounts for most ATP produced intracellularly. In addition, fermentation appeared to be totally blocked thus leaving no chance of the infected cells regenerating NAD. Concurrent increase in cAMP concentration within the first hour of infection may contribute to the rapid and efficient cell killing. Cells infected by BS176 always showed an intermediate phenotype (i.e. ATP depletion, pyruvate increase, lactate decrease). Early lysis of the phagocytic vacuole by M90T may account for this difference by allowing toxic products of the bacteria to diffuse more efficiently within the cytosol.
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PMID:Metabolic events mediating early killing of host cells infected by Shigella flexneri. 284 71

FliI is a Salmonella typhimurium protein that is needed for flagellar assembly and may be involved in a specialized protein export pathway that proceeds without signal peptide cleavage. FliI shows extensive sequence similarity to the catalytic beta subunit of the F0F1 ATPase (A. P. Volger, M. Homma, V. M. Irikura, and R. M. Macnab, J. Bacteriol. 173:3564-3572, 1991). It is even more similar to the Spa47 protein of Shigella flexneri (M. M. Venkatesan, J. M. Buysse, and E. V. Oaks, J. Bacteriol. 174:1990-2001, 1992) and the HrpB6 protein of Xanthomonas campestris (S. Fenselau, I. Balbo, and U. Bonas, Mol. Plant-Microbe Interact. 5:390-396, 1992), which are believed to play a role in the export of virulence proteins. Site-directed mutagenesis of residues in FliI that correspond to catalytically important residues in the F1 beta subunit resulted in loss of flagellation, supporting the hypothesis that FliI is an ATPase. FliI was overproduced and purified almost to homogeneity. It demonstrated ATP binding but not hydrolysis. An antibody raised against FliI permitted detection of the protein in wild-type cells and an estimate of about 1,500 subunits per cell. An antibody directed against the F1 beta subunit of Escherichia coli cross-reacted with FliI, confirming that the proteins are structurally related. The relationship between three proteins involved in flagellar assembly (FliI, FlhA, and FliP) and homologs in a variety of virulence systems is discussed.
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PMID:Genetic and biochemical analysis of Salmonella typhimurium FliI, a flagellar protein related to the catalytic subunit of the F0F1 ATPase and to virulence proteins of mammalian and plant pathogens. 849 29

Once in the cytoplasm of mammalian cells, Shigella flexneri expresses a motile phenotype caused by polar directional assembly of actin. This process depends on accumulation of IcsA (VirG), a 120-kDa protein with ATPase activity, at the pole of the bacterium opposite to that at which ongoing septation occurs. IcsA is also secreted into the bacterial supernatant as a 95-kDa species, after cleavage at an SSRRASS sequence which, when mutagenized, blocks processing. MAbF15, an anti-IcsA monoclonal antibody, recognizes an epitope located within repeated Gly-rich boxes in the N-terminal half of the protein. We used this monoclonal antibody to visualize the location of a noncleavable 120-kDa IcsA mutant protein expressed in S. flexneri. We found that this noncleavable IcsA protein no longer localized exclusively to the pole of the bacterium but also could be detected circumferentially. Whereas the monoclonal antibody detected the wild-type cleavable form of IcsA in only 40% of the cells expressing this protein, the noncleavable was easily detectable in all the cells carrying the icsA mutant allele. Similar aberrant localization of the IcsA mutant protein on bacteria growing within the cytoplasm of HeLa cells was observed. The strains expressing the noncleavable IcsA protein expressed abnormal intracellular movement and were often observed moving in a direction perpendicular to their longitudinal axis. The putative protease which processes IcsA may therefore play a role in achieving polar expression of this protein and providing maximum asymmetry essential to directional movement. In addition, MAbF15 allowed us to identify a 70-kDa eukaryotic protein cross-reacting with IcsA. This protein accumulated in the actin tails of motile bacteria and in membrane ruffles of the cells.
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PMID:Lack of cleavage of IcsA in Shigella flexneri causes aberrant movement and allows demonstration of a cross-reactive eukaryotic protein. 855 Feb

A differential PCR technique detected the transcriptional downregulation of the mss1 (mammalian suppressor of svg1) gene in murine J774A.1 macrophages following uptake of Salmonella typhimurium. This downregulation was also noted after entry of virulent strains of Listeria monocytogenes and Shigella flexneri, two other facultative intracellular bacterial species. In contrast, uptake of nonpathogenic Escherichia coli HB101, an aroA mutant of S. typhimurium, an invasion plasmid antigen B (ipaB) mutant of S. flexneri, hemolysin (hly) and positive-regulatory factor (prfA) mutants of L. monocytogenes, or latex beads produced mss1 expression levels similar to that of uninfected macrophages. Transcriptional downregulation of mss1 was also shown to occur in S. typhimurium-infected human U937 cells, albeit to an extent less than that in murine J774A.1 cells. In addition to a lower abundance of mss1 transcripts, we also demonstrate for the first time that less MSS1 protein was detected in intracellular-bacterium-infected cells (beginning about 1 h after entry of the pathogenic intracellular bacteria) than in noninfected cells. Some strains with specific mutations in characterized genes, such as an ipaB mutant strain of S. flexneri and an hly mutant strain of L. monocytogenes, did not elicit this lower level of expression of MSS1 protein. The decrease in MSS1 within infected macrophages resulted in an accumulation of ubiquitinated proteins, substrates for MSS1. Since MSS1 comprises the ATPase part of the 26S protease that degrades ubiquitinated proteins, we hypothesize that downregulation of the mss1 gene by intracellular bacterial entry may help subvert the host cell's normal defensive response to internalized bacteria, allowing the intracellular bacteria to survive.
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PMID:Uptake of pathogenic intracellular bacteria into human and murine macrophages downregulates the eukaryotic 26S protease complex ATPase gene. 935 61

The Gram-negative enteric bacterium Proteus mirabilis is a frequent cause of urinary tract infections (UTIs) in individuals with long-term indwelling catheters or with complicated urinary tracts. The recent release of the P. mirabilis strain HI4320 genome sequence has facilitated identification of potential virulence factors in this organism. Genes appearing to encode a type III secretion system (TTSS) were found in a low GC-content pathogenicity island in the P. mirabilis chromosome. This island contains 24 intact genes that appear to encode all components necessary to assemble a TTSS needle complex, plus at least two putative secreted effector proteins and their chaperones. The genetic organization of the TTSS genes is very similar to that of the TTSS of Shigella flexneri. RT-PCR analysis indicated that these genes are expressed at low levels in vitro. However, insertional mutation of two putative TTSS genes, encoding the requisite ATPase and a possible negative regulator, resulted in no change in either the growth rate of the mutant or the secreted protein profile compared to wild-type. Furthermore, there was no difference in quantitative cultures of urine, bladder and kidney between the ATPase mutant and the wild-type strain in the mouse model of ascending UTI in either independent challenge or co-challenge experiments. The role of the P. mirabilis TTSS, if any, is yet to be determined.
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PMID:The type III secretion system of Proteus mirabilis HI4320 does not contribute to virulence in the mouse model of ascending urinary tract infection. 1789 61

The conserved ATPase of type III secretion systems is critical to the export of substrates through the apparatus. We present a characterization of the native T3SS ATPase, Spa47, from the cytoplasm of Shigella flexneri, demonstrating it to be in two distinct high-molecular-weight complexes with Spa33: MxiN and MxiK.
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PMID:Characterization of soluble complexes of the Shigella flexneri type III secretion system ATPase. 1865 9

Many gram-negative pathogenic bacteria use a type III secretion (T3S) system to interact with cells of their hosts. Mechanisms controlling the hierarchical addressing of needle subunits, translocators and effectors to the T3S apparatus (T3SA) are still poorly understood. We investigated the function of MxiC, the member of the YopN/InvE/SepL family in the Shigella flexneri T3S system. Inactivation of mxiC led specifically to a deregulated secretion of effectors (including IpaA, IpgD, IcsB, IpgB2, OspD1 and IpaHs), but not of translocators (IpaB and IpaC) and proteins controlling the T3SA structure or activity (Spa32 and IpaD). Expression of effector-encoding genes controlled by the activity of the T3SA and the transcription activator MxiE was increased in the mxiC mutant, as a consequence of the increased secretion of the MxiE anti-activator OspD1. MxiC is a T3SA substrate and its ability to be secreted is required for its function. By using co-purification assays, we found that MxiC can associate with the Spa47 ATPase, which suggests that MxiC might prevent secretion of effectors by blocking the T3SA from the inside. Although with a 10-fold reduced efficiency compared with the wild-type strain, the mxiC mutant was still able to enter epithelial cells.
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PMID:MxiC is secreted by and controls the substrate specificity of the Shigella flexneri type III secretion apparatus. 1901 68

Many Gram-negative bacteria initiate infections by injecting effector proteins into host cells through the type III secretion apparatus, which is comprised of a basal body, a needle, and a tip. The needle channel is formed by the assembly of a single needle protein. To explore the export mechanisms of MxiH needle protein through the needle of Shigella flexneri, an essential step during needle assembly, we have performed steered molecular dynamics simulations in implicit solvent. The trajectories reveal a screwlike rotation motion during the export of nativelike helix-turn-helix conformations. Interestingly, the channel interior with excessive electronegative potential creates an energy barrier for MxiH to enter the channel, whereas the same may facilitate the ejection of the effectors into host cells. Structurally known basal regions and ATPase underneath the basal region also have electronegative interiors. Effector proteins also have considerable electronegative potential patches on their surfaces. From these observations, we propose a repulsive electrostatic mechanism for protein translocation through the type III secretion apparatus. Based on this mechanism, the ATPase activity and/or proton motive force could be used to energize the protein translocation through these nanomachines. A similar mechanism may be applicable to macromolecular channels in other secretion systems or viruses through which proteins or nucleic acids are transported.
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PMID:A repulsive electrostatic mechanism for protein export through the type III secretion apparatus. 2014 59


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