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

---

Query: EC:3.6.3.1 (Mg2+-ATPase)
1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Shiga toxigenic Escherichia coli (STEC) strains are a diverse group of organisms capable of causing severe gastrointestinal disease in humans. Within the STEC family, eae-positive STEC strains, particularly those belonging to serogroups O157 and O111, appear to have greater virulence for humans. However, in spite of being eae negative, STEC strains belonging to serogroup O113 have frequently been associated with cases of severe STEC disease, including hemolytic-uremic syndrome (HUS). Western blot analysis with convalescent-phase serum from a patient with HUS caused by an O113:H21 STEC strain indicated that human immune responses were directed principally against lipopolysaccharide O antigen. Accordingly, the serum was used to isolate a clone expressing O113 O antigen from a cosmid library of O113:H21 DNA constructed in E. coli K-12. Sequence analysis indicated that the O113 O-antigen biosynthesis (rfb) locus contains a cluster of nine genes which may be cotranscribed. Comparison with sequence databases identified candidate genes for four glycosyl transferases, an O-acetyl transferase, an O-unit flippase, and an O-antigen polymerase, as well as copies of galE and gnd. Two additional, separately transcribed genes downstream of the O113 rfb region were predicted to encode enzymes involved in synthesis of activated sugar precursors, one of which (designated wbnF) was essential for O113 O-antigen synthesis, and so is clearly a part of the O113 rfb locus. Interestingly, expression of O113 O antigen by E. coli K-12 significantly increased in vitro adherence to both HEp-2 and Henle 407 cells.
...
PMID:Molecular characterization of the locus encoding biosynthesis of the lipopolysaccharide O antigen of Escherichia coli serotype O113. 1053 Dec 50

The lipopolysaccharide (LPS) O-antigen of Yersinia enterocolitica serotype O:8 is formed by branched pentasaccharide repeat units that contain N-acetylgalactosamine (GalNAc), L-fucose (Fuc), D-galactose (Gal), D-mannose (Man), and 6-deoxy-D-gulose (6d-Gul). Its biosynthesis requires at least enzymes for the synthesis of each nucleoside diphosphate-activated sugar precursor; five glycosyltransferases, one for each sugar residue; a flippase (Wzx); and an O-antigen polymerase (Wzy). As this LPS shows a characteristic preferred O-antigen chain length, the presence of a chain length determinant protein (Wzz) is also expected. By targeted mutagenesis, we identify within the O-antigen gene cluster the genes encoding Wzy and Wzz. We also present genetic and biochemical evidence showing that the gene previously called galE encodes a UDP-N-acetylglucosamine-4-epimerase (EC 5.1.3.7) required for the biosynthesis of the first sugar of the O-unit. Accordingly, the gene was renamed gne. Gne also has some UDP-glucose-4-epimerase (EC 5.1.3.2) activity, as it restores the core production of an Escherichia coli K-12 galE mutant. The three-dimensional structure of Gne was modeled based on the crystal structure of E. coli GalE. Detailed structural comparison of the active sites of Gne and GalE revealed that additional space is required to accommodate the N-acetyl group in Gne and that this space is occupied by two Tyr residues in GalE whereas the corresponding residues present in Gne are Leu136 and Cys297. The Gne Leu136Tyr and Cys297Tyr variants completely lost the UDP-N-acetylglucosamine-4-epimerase activity while retaining the ability to complement the LPS phenotype of the E. coli galE mutant. Finally, we report that Yersinia Wzx has relaxed specificity for the translocated oligosaccharide, contrary to Wzy, which is strictly specific for the O-unit to be polymerized.
...
PMID:Functional characterization of Gne (UDP-N-acetylglucosamine-4-epimerase), Wzz (chain length determinant), and Wzy (O-antigen polymerase) of Yersinia enterocolitica serotype O:8. 1210 46

Escherichia coli MsbA, the proposed inner membrane lipid flippase, is an essential ATP-binding cassette transporter protein with homology to mammalian multidrug resistance proteins. Depletion or loss of function of MsbA results in the accumulation of lipopolysaccharide and phospholipids in the inner membrane of E. coli. MsbA modified with an N-terminal hexahistidine tag was overexpressed, solubilized with a nonionic detergent, and purified by nickel affinity chromatography to approximately 95% purity. The ATPase activity of the purified protein was stimulated by phospholipids. When reconstituted into liposomes prepared from E. coli phospholipids, MsbA displayed an apparent K(m) of 878 microm and a V(max) of 37 nmol/min/mg for ATP hydrolysis in the presence of 10 mm Mg(2+). Preincubation of MsbA-containing liposomes with 3-deoxy-d-mannooctulosonic acid (Kdo)(2)-lipid A increased the ATPase activity 4-5-fold, with half-maximal stimulation seen at 21 microm Kdo(2)-lipid A. Addition of Kdo(2)-lipid A increased the V(max) to 154 nmol/min/mg and decreased the K(m) to 379 microm. Stimulation was only seen with hexaacylated lipid A species and not with precursors, such as diacylated lipid X or tetraacylated lipid IV(A). MsbA containing the A270T substitution, which renders cells temperature-sensitive for growth and lipid export, displayed ATPase activity similar to that of the wild type protein at 30 degrees C but was significantly reduced at 42 degrees C. These results provide the first in vitro evidence that MsbA is a lipid-activated ATPase and that hexaacylated lipid A is an especially potent activator.
...
PMID:ATPase activity of the MsbA lipid flippase of Escherichia coli. 1211 3

Shigella is an important human pathogen. It is generally agreed that Shigella and Escherichia coli constitute a single species; the only exception is Shigella boydii type 13, which is more distantly related to E. coli and other Shigella forms and seems to represent another species. This gives S. boydii type 13 an important status in evolution. O antigen is the polysaccharide part of the lipopolysaccharide in the outer membrane of gram-negative bacteria and plays an important role in pathogenicity. The chemical structure and genetic organization of the S. boydii type 13 O antigen were investigated. The O polysaccharide was found to be acid labile owing to the presence of a glycosyl phosphate linkage in the main chain. The structure of the linear pentasaccharide phosphate repeating unit (O unit) was established by nuclear magnetic resonance spectroscopy, including two-dimensional COSY, TOCSY, ROESY, and H-detected 1H, 13C and 1H, 31P HMQC experiments, along with chemical methods. The O antigen gene cluster of S. boydii type 13 was located and sequenced. Genes for synthesis of UDP-2-acetamido-2,6-dideoxy-L-glucose and genes that encode putative sugar transferases, O unit flippase, and O antigen polymerase were identified. Seven genes were found to be specific to S. boydii type 13. The S. boydii type 13 O antigen gene cluster has higher levels of sequence similarity with Vibrio cholerae gene clusters and may be evolutionarily related to these gene clusters.
...
PMID:Structural and genetic characterization of the Shigella boydii type 13 O antigen. 1470 7

Shigella is an important human pathogen and is closely related to Escherichia coli. O-antigen is the most variable part of the lipopolysaccharide on the cell surface of Gram-negative bacteria and plays an important role in pathogenicity. The O-antigen gene cluster of S. boydii O1 was sequenced. The putative genes encoding enzymes for rhamnose synthesis, transferases, O-unit flippase, and O-unit polymerase were identified on the basis of homology. The O-antigen gene clusters of S. boydii O1 and E. coli O149, which share the same O-antigen form, were found to have the same genes and organization by adjacent gene PCR assay. Two genes specific for S. boydii O1 and E. coli O149 were identified by PCR screening against E. coli- and Shigella-type strains of the 186 known O-antigen forms and 39 E. coli clinical isolates. A PCR sensitivity of 103 to 104 CFU/mL overnight culture of S. boydii O1 and E. coli O149 was obtained. S. boydii O1 and E. coli O149 were differentiated by PCR using lacZ- and cadA-based primers.
...
PMID:Molecular analysis of Shigella boydii O1 O-antigen gene cluster and its PCR typing. 1608 33

Translocation of lipid-linked oligosaccharide (LLO) intermediates across membranes is an essential but poorly understood process in eukaryotic and bacterial glycosylation pathways. Membrane proteins defined as translocases or flippases are implicated to mediate the translocation reaction. The membrane protein Wzx has been proposed to mediate the translocation across the plasma membrane of lipopolysaccharide (LPS) O antigen subunits, which are assembled on an undecaprenyl pyrophosphate lipid carrier. Similarly, PglK (formerly WlaB) is a Campylobacter jejuni-encoded ABC-type transporter proposed to mediate the translocation of the undecaprenylpyrophosphate-linked heptasaccharide intermediate involved in the recently identified bacterial N-linked protein glycosylation pathway. A combination of genetic and carbohydrate structural analyses defined and characterized flippase activities in the C. jejuni N-linked protein glycosylation and the Escherichia coli LPS O antigen biosynthesis. PglK displayed relaxed substrate specificity with respect to the oligosaccharide structure of the LLO intermediate and complemented a wzx deficiency in E. coli O-antigen biosynthesis. Our experiments provide strong genetic evidence that LLO translocation across membranes can be catalyzed by two distinct proteins that do not share any sequence similarity.
...
PMID:Two distinct but interchangeable mechanisms for flipping of lipid-linked oligosaccharides. 1649

The DNA sequence of the O antigen gene cluster of an Escherichia coli serogroup O118 strain was determined, and 13 open reading frames (ORFs) were identified, encoding genes required for O antigen sugar biosynthesis, transfer, and processing. Polymerase chain reaction (PCR) assays targeting the wzx (O antigen flippase) and wzy (O antigen polymerase) genes in the O antigen gene cluster of E. coli O118 were designed for identification of these serogroups. Specificity testing using strains belonging to E. coli O118 isolated from various sources, representative strains of 167 other E. coli O serogroups, and 20 non-E. coli bacteria revealed that the PCR assays were specific for E. coli O118. Thus, the PCR assays can be used for rapid identification of E. coli O118 as an alterative to typing using antisera. However, the PCR assays targeting the E. coli O118 wzx and wzy genes were also positive using E. coli serogroup O151 DNA. Therefore, the sequence of the O antigen gene cluster of E. coli O151 was determined, and it was very similar to that of E. coli O118, with only three nucleotide differences. Although the lipopolysaccharide profiles of O118 and O151 showed differences, multilocus sequence typing of E. coli O118 and O151 strains only revealed minor variation at the nucleotide level. Since E. coli O118 strains are more frequently isolated from humans, animals, and the environment than E. coli O151, serogroup O151 may likely be a minor variant of E. coli O118. Further studies are needed to elucidate this possibility.
...
PMID:DNA sequencing and identification of serogroup-specific genes in the Escherichia coli O118 O antigen gene cluster and demonstration of antigenic diversity but only minor variation in DNA sequence of the O antigen clusters of E. coli O118 and O151. 1867 69

Aeromonas caviae Sch3N possesses a small genomic island that is involved in both flagellin glycosylation and lipopolysaccharide (LPS) O-antigen biosynthesis. This island appears to have been laterally acquired as it is flanked by insertion element-like sequences and has a much lower G+C content than the average aeromonad G+C content. Most of the gene products encoded by the island are orthologues of proteins that have been shown to be involved in pseudaminic acid biosynthesis and flagellin glycosylation in both Campylobacter jejuni and Helicobacter pylori. Two of the genes, lst and lsg, are LPS specific as mutation of them results in the loss of only a band for the LPS O-antigen. Lsg encodes a putative Wzx flippase, and mutation of Lsg affects only LPS; this finding supports the notion that flagellin glycosylation occurs within the cell before the flagellins are exported and assembled and not at the surface once the sugar has been exported. The proteins encoded by flmA, flmB, neuA, flmD, and neuB are thought to make up a pseudaminic acid biosynthetic pathway, and mutation of any of these genes resulted in the loss of motility, flagellar expression, and a band for the LPS O-antigen. Furthermore, pseudaminic acid was shown to be present on both flagellin subunits that make up the polar flagellum filament, to be present in the LPS O-antigen of the A. caviae wild-type strain, and to be absent from the A. caviae flmD mutant strain.
...
PMID:An Aeromonas caviae genomic island is required for both O-antigen lipopolysaccharide biosynthesis and flagellin glycosylation. 1921 87

Escherichia coli mutants deficient in 2-keto-3-deoxy-D-manno-octulosonic acid (Kdo) biosynthesis are conditionally lethal, but their phenotypes are bypassed by certain suppressor mutations or by overexpression of MsbA, the inner membrane flippase for core-lipid A. These strains grow on broth with the tetraacylated precursor lipid IV(A) replacing lipopolysaccharide [Meredith, T. C., et al. (2006) ACS Chem. Biol. 1, 33-42]. Deletion of kdtA, which encodes the Kdo transferase, is possible under these conditions. We now show that lipid IV(A) reaches the outer surface of the outer membrane in these strains, as judged by its accessibility to the lipase PagL. On the assumption that MsbA is optimized to transport penta- or hexaacylated lipid A, we overexpressed the lauroyl- or the myristoyltransferase of lipid A biosynthesis, encoded by lpxL and lpxM, respectively, and demonstrated that kdtA deletion mutants were also viable in this setting. Although E. coli LpxL is stimulated by the presence of the Kdo disaccharide in its acceptor substrate, LpxL does slowly acylate lipid IV(A). Overexpression of LpxL from a plasmid suppressed the lethality of kdtA deletions on nutrient broth at 30 or 37 degrees C without the need for MsbA overproduction. These strains accumulated penta- and hexaacylated free lipid A containing a secondary laurate chain or a laurate and a myristate chain, respectively. Deletion of kdtA in strains overexpressing LpxM accumulated pentaacylated lipid A with a secondary myristate moiety. None of the strains lacking kdtA grew in the presence of bile salts at any temperature or on nutrient broth at 42 degrees C. Our findings show that the main function of Kdo is to provide the right substrates for the acyltransferases LpxL and LpxM, resulting in the synthesis of penta- and hexaacylated lipid A, which is optimal for the MsbA flippase.
...
PMID:Replacement of lipopolysaccharide with free lipid A molecules in Escherichia coli mutants lacking all core sugars. 1975 49

The O-antigen is an essential component of lipopolysaccharide on the surface of Gram-negative bacteria and plays an important role in its pathogenicity. Composition and structure of the O-antigens of Escherichia coli are highly diverse mainly due to genetic variations in the O-antigen gene cluster. In this work, the chemical structure and the gene cluster of the O-antigen of E. coli O161 were studied. Chemical degradations, sugar analyses, and NMR spectroscopy showed that the O161 antigen possesses a trisaccharide O-repeating unit containing a 5-N-acetyl-7-N-(d-alanyl) derivative of 5,7-diamino-3,5,7,9-tetradeoxy-d-glycero-d-galacto-non-2-ulosonic (legionaminic) acid (Leg5Ac7Ala) and having the following structure: The O-antigen gene cluster of E. coli O161 was sequenced. In addition to the genes encoding sugar transferases, O-repeating unit flippase (Wzx) and O-antigen polymerase (Wzy), the genes involved in the biosynthesis of a legionaminic acid derivative were identified based on database similarities.
...
PMID:Structural and genetic characterization of the O-antigen of Escherichia coli O161 containing a derivative of a higher acidic diamino sugar, legionaminic acid. 2051 Mar 95


1 2 Next >>

---