John M, Röhrig H, Schmidt J, Wieneke U, Schell J
Max-Planck-Insitut für Züchtungsforschung, Köln, Federal Republic of Germany.
Proc Natl Acad Sci U S A. 1993 Jan 15;90(2):625-9. doi: 10.1073/pnas.90.2.625.
The common nodulation genes nodABC are conserved in all rhizobia and are involved in synthesis of a lipooligosaccharide signal molecule. This bacterial signal consists of a chitooligosaccharide backbone, which carries at the nonreducing end a fatty acyl chain. The modified chitooligosaccharide molecule triggers development of nodules on the roots of the leguminous host plant. To elucidate the specific role of the NodB protein in nodulation factor synthesis, we have purified recombinant NodB and determined its biochemical role by direct assays. Our data show that the NodB protein of Rhizobium meliloti deacetylates the nonreducing N-acetylglucosamine residue of chitooligosaccharides. The monosaccharide N-acetylglucosamine is not deacetylated by NodB. In the pathway of Nod factor synthesis, deacetylation at the nonreducing end of the oligosaccharide backbone may be a necessary requirement for attachment of the fatty acyl chain.
常见的结瘤基因nodABC在所有根瘤菌中都是保守的，并且参与脂寡糖信号分子的合成。这种细菌信号由一个壳寡糖主链组成，该主链在非还原端带有一条脂肪酰链。这种修饰的壳寡糖分子触发豆科宿主植物根上根瘤的形成。为了阐明NodB蛋白在结瘤因子合成中的具体作用，我们纯化了重组NodB，并通过直接测定确定了其生化作用。我们的数据表明，苜蓿根瘤菌的NodB蛋白使壳寡糖的非还原N-乙酰葡糖胺残基脱乙酰化。单糖N-乙酰葡糖胺不会被NodB脱乙酰化。在结瘤因子合成途径中，寡糖主链非还原端的脱乙酰化可能是脂肪酰链连接的必要条件。
