Max-Planck-Institut für Züchtungsforschung, Abt. Schell, D-5000 Köln 30, FRG.
EMBO J. 1984 Aug;3(8):1705-11. doi: 10.1002/j.1460-2075.1984.tb02035.x.
An 8.5-kb EcoRI fragment containing the common nod region of the megaplasmid pRme41b of Rhizobium meliloti was recloned in plasmids of Escherichia coli, and a detailed restriction map was established. The region can express at least eight proteins in E. coli minicells and in an in vitro transcription/translation system, prepared from E. coli. Protein coding regions were determined by subcloning of restriction fragments, deletion mutations and by transposon mutagenesis. The coding regions for at least three polypeptide chains (mol. wts. 23 000, 28 500 and 44 000) were mapped on a 3.3-kb nod gene cluster. The 44 000 mol. wt. protein is expressed from a nod region, which is highly conserved in two Rhizobium species. The protein map of the 8.5-kb fragment was correlated to a map of insertion mutations with Nod and Fix phenotypes. The data suggest that the proteins encoded by the nod gene cluster may be involved in early steps of the nodulation process. Nod Fix symbiotic mutations were localized in the coding region for a 33 000 mol. wt. protein, suggesting that this polypeptide might be a fix gene product.
一个包含 Rhizobium meliloti 巨型质粒 pRme41b 的共同结瘤区的 8.5kb EcoRI 片段被重新克隆到大肠杆菌的质粒中，并建立了详细的限制图谱。该区域至少可在大肠杆菌小型细胞和体外转录/翻译系统中表达 8 种蛋白质，该系统由大肠杆菌制备。通过亚克隆限制片段、缺失突变和转座子诱变来确定编码区。至少三个多肽链（分子量 23000、28500 和 44000）的编码区被映射到一个 3.3kb 的结瘤基因簇上。44000 分子量的蛋白质是从一个在两个 Rhizobium 物种中高度保守的结瘤区表达的。8.5kb 片段的蛋白质图谱与具有 Nod 和 Fix 表型的插入突变图谱相关联。这些数据表明，结瘤基因簇编码的蛋白质可能参与了结瘤过程的早期步骤。Nod Fix 共生突变定位于分子量为 33000 的蛋白质的编码区，表明该多肽可能是一个 Fix 基因产物。
