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genetic analysis of chromosomal mutations in the polysialic acid gene cluster of escherichia coli k1.the kps gene cluster of escherichia coli k1 encodes functions for sialic acid synthesis, activation, polymerization, and possibly translocation of polymer to the cell surface. the size and complexity of this membrane polysaccharide biosynthetic cluster have hindered genetic mapping and functional descriptions of the kps genes. to begin a detailed investigation of the polysialic acid synthetic mechanism, acapsular mutants were characterized to determine their probable defects in polymer synthesis ...19892644224
proteolytic release of the intramolecular chaperone domain confers processivity to endosialidase f.endosialidases (endons), as identified so far, are tailspike proteins of bacteriophages that specifically bind and degrade the alpha2,8-linked polysialic acid (polysia) capsules of their hosts. the crystal structure solved for the catalytic domain of endon from coliphage k1f (endonf) revealed a functional trimer. folding of the catalytic trimer is mediated by an intramolecular c-terminal chaperone domain. release of the chaperone from the folded protein confers kinetic stability to endonf. in mu ...200919189967
protein synthesis is required for in vivo activation of polysialic acid capsule synthesis in escherichia coli k1.the kinetics of in vivo expression of the polysialosyl (k1) capsular antigen in escherichia coli has been studied. growth of e. coli k1 strains at 15 degrees c prevents k1 polysaccharide synthesis (f. a. troy and m. a. mccloskey, j. biol. chem. 254:7377-7387, 1979). synthesis is reactivated in cells grown at 15 degrees c after upshift to 37 degrees c. the early expression and resultant morphology of k1 capsular antigen was monitored in temperature upshift experiments by using electron microscopy ...19846376473
selective synthesis and labeling of the polysialic acid capsule in escherichia coli k1 strains with mutations in nana and neub.the enzymes required for polysialic acid capsule synthesis in escherichia coli k1 are encoded by region 2 neu genes of the multigenic kps cluster. to facilitate analysis of capsule synthesis and translocation, an e. coli k1 strain with mutations in nana and neub, affecting sialic acid degradation and synthesis, respectively, was constructed by transduction. the acapsular phenotype of the mutant was corrected in vivo by exogenous addition of sialic acid. by blocking sialic acid degradation, the n ...19921400168
structural basis for the recognition and cleavage of polysialic acid by the bacteriophage k1f tailspike protein endonf.an alpha-2,8-linked polysialic acid (polysia) capsule confers immune tolerance to neuroinvasive, pathogenic prokaryotes such as escherichia coli k1 and neisseria meningitidis and supports host infection by means of molecular mimicry. bacteriophages of the k1 family, infecting e. coli k1, specifically recognize and degrade this polysia capsule utilizing tailspike endosialidases. while the crystal structure for the catalytic domain of the endosialidase of bacteriophage k1f (endonf) has been solved ...201020096705
the genome of bacteriophage k1f, a t7-like phage that has acquired the ability to replicate on k1 strains of escherichia coli.bacteriophage k1f specifically infects escherichia coli strains that produce the k1 polysaccharide capsule. like several other k1 capsule-specific phages, k1f encodes an endo-neuraminidase (endosialidase) that is part of the tail structure which allows the phage to recognize and degrade the polysaccharide capsule. the complete nucleotide sequence of the k1f genome reveals that it is closely related to bacteriophage t7 in both genome organization and sequence similarity. the most striking differe ...200516321955
structure of a group a streptococcal phage-encoded virulence factor reveals a catalytically active triple-stranded beta-helix.streptococcus pyogenes (group a streptococcus) causes severe invasive infections including scarlet fever, pharyngitis (streptococcal sore throat), skin infections, necrotizing fasciitis (flesh-eating disease), septicemia, erysipelas, cellulitis, acute rheumatic fever, and toxic shock. the conversion from nonpathogenic to toxigenic strains of s. pyogenes is frequently mediated by bacteriophage infection. one of the key bacteriophage-encoded virulence factors is a putative "hyaluronidase," hylp1, ...200516314578
identification of polysialic acid-containing glycoprotein in the jelly coat of sea urchin eggs. occurrence of a novel type of polysialic acid structure.sea urchin eggs are surrounded by a gelatinous layer (called the jelly coat) that consists of mixture of fucoserich polysaccharides and sialic acid-rich glycoproteins. chemical and 500 mhz 1h nmr spectroscopic studies revealed for the first time the presence of a novel polysialic acid (polysia) structure in the jelly coat glycoproteins isolated from hemicentrotus pulcherrimus (designated polysia-gp(h)). the structure of the polysia chains was thoroughly characterized as (-->5-oglycolyl-neu5gc al ...19948077223
reduced polysialic acid capsule expression in escherichia coli k1 mutants with chromosomal defects in kpsf.neuroinvasive escherichia coli k1 synthesizes and assembles a polysialic acid capsule virulence factor on the external leaflet of the outer membrane. this capsule functions in pathogenesis by blocking non-immune host defence mechanisms and acting as a relatively non-immunogenic molecular mimic of the polysialic acid chains found in high concentrations on neural cell adhesion molecules of the human embryo and neonate. the synthetic, regulatory and export components for capsule expression are enco ...19979383150
complete nucleotide sequence of the bacteriophage k1f tail gene encoding endo-n-acylneuraminidase (endo-n) and comparison to an endo-n homolog in bacteriophage pk1e.endo-n-acylneuraminidase (endo-n) is a phage-encoded depolymerase that degrades the alpha (2-8)-linked polysialic acid chains of k1 serotypes of escherichia coli and vertebrate neural cell adhesion molecules. we have determined the dna sequence of the bacteriophage k1f tail protein structural gene, which codes for a polypeptide of 920 residues. purification of the tail protein yields a 102-kda species upon denaturing gel electrophoresis and detection by western immunoblot analysis. an identical ...19938331067
crystal structure of the polysialic acid-degrading endosialidase of bacteriophage k1f.phages infecting the polysialic acid (polysia)-encapsulated human pathogen escherichia coli k1 are equipped with capsule-degrading tailspikes known as endosialidases, which are the only identified enzymes that specifically degrade polysia. as polysia also promotes cellular plasticity and tumor metastasis in vertebrates, endosialidases are widely applied in polysia-related neurosciences and cancer research. here we report the crystal structures of endosialidase nf and its complex with oligomeric ...200415608653
a new sialidase mechanism: bacteriophage k1f endo-sialidase is an inverting glycosidase.bacteriophages specific for escherichia coli k1 express a tailspike protein that degrades the polysialic acid coat of e. coli k1 that is essential for bacteriophage infection. this enzyme is specific for polysialic acid and is a member of a family of endo-sialidases. this family is unusual because all other previously reported sialidases outside of this family are exo- or trans-sialidases. the recently determined structure of an endo-sialidase derived from bacteriophage k1f (endonf) revealed an ...200919411257
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