Ozaki Kazuhisa, Shibata Yukie, Yamashita Yoshihisa, Nakano Yoshio, Tsuda Hiromasa, Koga Toshihiko
Department of Preventive Dentistry, Kyushu University Faculty of Dental Science, Fukuoka 812-8582, Japan.
FEBS Lett. 2002 Dec 4;532(1-2):159-63. doi: 10.1016/s0014-5793(02)03661-x.
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.
我们克隆了两个基因（rgpH和rgpI），它们编码参与变形链球菌鼠李糖 - 葡萄糖多糖（RGP）葡萄糖侧链形成的蛋白质，RGP由带有葡萄糖侧链的鼠李聚糖主链组成。在合成鼠李聚糖的大肠杆菌中评估了rgpH和rgpI的作用。携带rgpH的大肠杆菌菌株与针对完整RGP的抗血清发生反应，而携带rgpI的大肠杆菌菌株则不与该抗血清反应。尽管大肠杆菌：rgpH与鼠李聚糖特异性抗血清强烈反应，但该菌株与rgpI共转化增加了葡萄糖侧链的数量，并显著降低了与鼠李聚糖特异性抗血清的免疫反应性。这些结果表明，在大肠杆菌中变形链球菌RGP合成过程中，两个基因参与侧链形成：一个基因编码葡糖基转移酶，另一个基因可能控制分支频率。这是首次报道鉴定出参与多糖合成中分支频率调控的基因。
