BacS:: An abundant bacteroid protein in Rhizobium etli whose expression ex planta requires nifA
BacS:: An abundant bacteroid protein in Rhizobium etli whose expression ex planta requires nifA
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DOI：
10.1094/mpmi.2003.16.1.65
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发表时间：
2003-01-01
影响因子：
3.5
通讯作者：
Noel, KD
中科院分区：
文献类型：
--
作者：
Jahn, OJ;Davila, G;Noel, KD
根瘤菌etli CFN 42类杆菌从豆根瘤具有丰富的16 kDa的蛋白质（BacS），被发现在细胞破碎后的膜沉淀。在胰蛋白胨-酵母提取物中培养的细菌中未检测到该蛋白。在基本培养基中，它产生在低氧浓度，但不是在突变体的nifA被破坏。蛋白质的N-末端测序导致bacS DNA片段的分离。DNA杂交和核苷酸测序揭示了三个拷贝的bacS基因，所有驻留在菌株CFN 42的主要共生质粒上。一段304个核苷酸，在所有三个bacS开放阅读框的上游完全保守，与NifA和sigma 54共有结合序列非常接近。基因序列数据库中唯一的bacS同源性是三个假设的蛋白质的未知功能，所有根瘤菌物种。突变和遗传互补表明，每个bacS基因产生一个BacS多肽。在所有三个基因中被破坏或缺失的突变体不产生BacS多肽，但在菜豆上是Nod（+）和Fix（+）。
Rhizobium etli CFN42 bacteroids from bean nodules possessed an abundant 16-kDa protein (BacS) that was found in the membrane pellet after cell disruption. This protein was not detected in bacteria cultured in tryptone-yeast extract. In minimal media, it was produced at low oxygen concentration but not in a mutant whose nifA was disrupted. N-terminal sequencing of the protein led to isolation of a bacS DNA fragment. DNA hybridization and nucleotide sequencing revealed three copies of the bacS gene, all residing on the main symbiotic plasmid of strain CFN42. A stretch of 304 nucleotides, exactly conserved upstream of all three bacS open reading frames, had very close matches with the NifA and sigma 54 consensus binding sequences. The only bacS homology in the genetic sequence databases was to three hypothetical proteins of unknown function, all from rhizobial species. Mutation and genetic complementation indicated that each of the bacS genes gives rise to a BacS polypeptide. Mutants disrupted or deleted in all three genes did not produce the BacS polypeptide but were Nod(+) and Fix(+) on Phaseolus vulgaris.