Isolation and nucleotide sequence of the GDP-mannose:cellobiosyl-diphosphopolyprenol alpha-mannosyltransferase gene from Acetobacter xylinum.
A genetic locus from Acetobacter xylinum involved in acetan polysaccharide synthesis has been characterized. The chromosomal region was identified by screening a genomic library of A. xylinum in a Xanthomonas campestris mutant defective in xanthan polysaccharide synthesis. The A. xylinum cosmid clone can functionally complement a xanthan-negative mutant. The polymer produced by the recombinant strain was found to be indistinguishable from xanthan. Insertion mutagenesis and subcloning of the cosmid clone combined with complementation studies allowed the identification of a 2.3-kb fragment of A. xylinum chromosomal DNA. The nucleotide sequence of this fragment was analyzed and found to contain an open reading frame (aceA) of 1,182 bp encoding a protein of 43.2 kDa. Results from biochemical and genetic analyses strongly suggest that the aceA gene encodes the GDP-mannose:cellobiosyl-diphosphopolyprenol alpha-mannosyltransferase enzyme, which is responsible for the transfer of an alpha-mannosyl residue from GDP-Man to cellobiosyl-diphosphopolyprenol. A search for similarities with other known mannosyltransferases revealed that all bacterial alpha-mannosyltransferases have a short COOH-terminal amino acid sequence in common.
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Instituto de Investigaciones Bioquímicas Fundación Campomar, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
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D000465:Algorithms; D000595:Amino Acid Sequence; D002240:Carbohydrate Sequence; D003001:Cloning, Molecular; D003227:Conjugation, Genetic; D017124:Conserved Sequence; D004926:Escherichia coli; D015723:Gene Library; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D041822:Gluconacetobacter xylinus / Q000201:enzymology* / Q000235:genetics*; D008364:Mannosyltransferases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016366:Open Reading Frames; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014974:Xanthomonas / Q000235:genetics
D011135:Polysaccharides, Bacterial; D011994:Recombinant Proteins; C068545:acetan; C100893:GDP-mannose - cellobiosyl-diphosphopolyprenol mannosyltransferase; D008364:Mannosyltransferases; C002563:xanthan gum