de Maagd R A, Wijfjes A H, Spaink H P, Ruiz-Sainz J E, Wijffelman C A, Okker R J, Lugtenberg B J
Department of Plant Molecular Biology, Leiden University, The Netherlands.
J Bacteriol. 1989 Dec;171(12):6764-70. doi: 10.1128/jb.171.12.6764-6770.1989.
The region of the Rhizobium leguminosarum biovar viciae Sym plasmid pRL1JI, responsible for the production and secretion of a previously described 50-kilodalton protein (R. A. de Maagd, C. A. Wijffelman, E. Pees, and B. J. J. Lugtenberg, J. Bacteriol. 170:4424-4427, 1988), was cloned and its nucleotide sequence was determined. A new nod gene, nodO, preceded by a poorly conserved nod box, was identified and its transcriptional start site was determined. Comparison of its predicted protein product with the N-terminal amino acid sequence of the isolated secreted protein showed that nodO is the structural gene of this protein, although the nucleotide sequence predicted a protein only 30,002 daltons in size. This comparison also showed that the secreted protein is not the product of N-terminal processing of a larger precursor. A conventional N-terminal signal sequence was not detected in the NodO protein. The NodO protein has significant homology with a part (residues 720 to 920) of the hemolysin protein (HlyA) of Escherichia coli. Analysis of the transcriptional regulation of the nodO gene revealed that, in contrast with other nod promoters in this species, activity of the nodO promoter is greatly enhanced in the presence of multiple copies of the nodD gene.
豌豆根瘤菌生物变种蚕豆根瘤菌Sym质粒pRL1JI中负责产生和分泌一种先前描述的50千道尔顿蛋白质的区域（R.A.德马格德、C.A.维费尔曼、E.皮斯和B.J.J.卢滕贝格，《细菌学杂志》170:4424 - 4427，1988年）被克隆并测定了其核苷酸序列。一个新的结瘤基因nodO被鉴定出来，其前面有一个保守性较差的结瘤框，并确定了其转录起始位点。将其预测的蛋白质产物与分离出的分泌蛋白的N端氨基酸序列进行比较，结果表明nodO是该蛋白质的结构基因，尽管核苷酸序列预测的蛋白质大小仅为30,002道尔顿。这种比较还表明，分泌蛋白不是更大前体进行N端加工的产物。在NodO蛋白中未检测到传统的N端信号序列。NodO蛋白与大肠杆菌溶血素蛋白（HlyA）的一部分（第720至920位残基）具有显著同源性。对nodO基因转录调控的分析表明，与该物种中的其他结瘤启动子不同，在存在多个nodD基因拷贝的情况下，nodO启动子的活性大大增强。
