title: A novel mechanism for glucose side-chain formation in rhamnose-glucose polysaccharide synthesis.
abstract: We have cloned two genes (rgpH and rgpI) that encode proteins for the formation of the glucose side-chains of the Streptococcus mutans rhamnose-glucose polysaccharide (RGP), which consists of a rhamnan backbone with glucose side-chains. The roles of rgpH and rgpI were evaluated in a rhamnan-synthesizing Escherichia coli. An E. coli strain that harbored rgpH reacted with antiserum directed against complete RGP, whereas the E. coli strain that carried rgpI did not react with this antiserum. Although E. coli:rgpH reacted strongly with rhamnan-specific antiserum, co-transformation of this strain with rgpI increased the number of glucose side-chains and decreased immunoreactivity with the rhamnan-specific antiserum significantly. These results suggest that two genes are involved in side-chain formation during S. mutans RGP synthesis in E. coli: one gene encodes a glucosyltransferase, and the other gene probably controls the frequency of branching. This is the first report to identify a gene that is involved in regulation of branching frequency in polysaccharide synthesis.
authors.affiliation: Department of Preventive Dentistry, Kyushu University Faculty of Dental Science, Fukuoka 812-8582, Japan.
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Ozaki
authors.forename: Yukie
authors.initials: Y
authors.lastname: Shibata
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Nakano
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Tsuda
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Koga
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D005947:Glucose / Q000378:metabolism*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D011134:Polysaccharides / Q000096:biosynthesis* / Q000276:immunology; D012333:RNA, Messenger / Q000378:metabolism; D012210:Rhamnose / Q000378:metabolism*; D013295:Streptococcus mutans / Q000235:genetics / Q000378:metabolism*; D014169:Transformation, Bacterial
chemical_list: D001426:Bacterial Proteins; D011134:Polysaccharides; D012333:RNA, Messenger; D005964:Glucosyltransferases; D005947:Glucose; D012210:Rhamnose