Biosynthesis of a substituted cellulose from a mutant strain of Xanthomonas campestris.
In Xanthomonas campestris the genes involved in polysaccharide (xanthan) biosynthesis are located in a gene cluster (gum) of 16 kb. A Tn5 insertion mutant with a reduced slimy phenotype has been characterized. This mutant failed to produce the pentasaccharide repeating-unit of xanthan. Only three sugars were transferred to the prenyl phosphate intermediate. Several lines of evidence suggested that the lipid-associated saccharide was the trisaccharide reducing end of the pentasaccharide from the wild-type strain. This trisaccharide was built up from UDP-Glc and GDP-Man, and a glucose residue was at the reducing end, linked to an allylic prenol through a diphosphate bridge. Results from one- or two-stage reactions showed that the trisaccharide-P-P-polyprenol was the precursor of the polymer. This new polymer, a polytrisaccharide, was detected also in vivo. The transposon responsible for the mutation was located within gumK gene. Therefore, this gene encodes for the glycosyltransferase IV, which catalyses the transfer of glucuronic acid to the lipid-linked beta-D-Manp-(1-->3)-beta-D-Glcp-(1-->4)-beta-D-Glcp trisaccharide. A recombinant plasmid with the whole gum cluster restored the wild type phenotype.
Vojnov
Adrián A
AA
Instituto de Investigaciones Bioquijmicas Fundacion Campomar, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Cientijficas y Tecnicas, Av. Patricias Argentinas 435, 1405, Buenos Aires, Argentina
Bassi
Daniel E
DE
Daniels
Michael J
MJ
Dankert
Marcelo A
MA
D001426:Bacterial Proteins / Q000502:physiology; D002482:Cellulose / Q000096:biosynthesis* / Q000737:chemistry; D004251:DNA Transposable Elements / Q000502:physiology; D020723:Glucuronic Acid / Q000378:metabolism; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D009844:Oligosaccharides / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D016959:Xanthomonas campestris / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; C089843:GumD protein, Xanthomonas campestris; D008070:Lipopolysaccharides; D009844:Oligosaccharides; D011135:Polysaccharides, Bacterial; C023023:lipid-linked oligosaccharides; D020723:Glucuronic Acid; D002482:Cellulose; D016695:Glycosyltransferases; C002563:xanthan gum