CAS Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Acta Biochim Biophys Sin (Shanghai). 2013 Oct;45(10):806-16. doi: 10.1093/abbs/gmt081. Epub 2013 Aug 8.
The Leptospira interrogans genome encodes two copies of cheR genes and each of them is able to complement for the swarming defective phenotype of Escherichia coli cheR null mutant RP1254 to certain extent, while over-expression of either of them inhibits the swarming of the chemotactic wild-type E. coli strain, RP437. Therefore, both CheR1 and CheR2 ought to bear the methyltransferase activities, although CheR1 has only one instead of two conserved basic amino acid residues located on the positively charged face of α2-helix. When this residue as well as the Lys48 and Arg55 of CheR2 was mutated, none of the CheRs was able to maintain aforementioned complementation functions, suggesting their critical roles in recognition of methyl-accepting chemotaxis proteins similar to that of E. coli. Demonstrated by microarray assay, the expression of cheR1 in L. interrogans cultured at 28°C in Ellinghausen-McCullough-Johnson-Harris medium was significantly lower than the average transcription level of all other genes, while the transcription of cheR2 was significantly higher than that of cheR1 in accordance with real-time reverse transcriptase-polymerase chain reaction assay. Tandem MS-MS data mining for the proteome of the same culture detected 16 peptides derived from CheR2 but none from CheR1. Therefore, although both genes were shown to be functional in E. coli, the structurally more conserved CheR2 rather than CheR1 might be the major functional component of L. interrogans chemotaxis adaptation system under our laboratory culture conditions.
问号钩端螺旋体基因组编码两个 CheR 基因拷贝，每个拷贝都能在一定程度上互补大肠杆菌 cheR 缺失突变体 RP1254 的群集缺陷表型，而它们中的任何一个过表达都会抑制趋化性野生型大肠杆菌菌株 RP437 的群集。因此，CheR1 和 CheR2 都应该具有甲基转移酶活性，尽管 CheR1 只有一个而不是两个位于α2-螺旋正电荷面上的保守碱性氨基酸残基。当这个残基以及 CheR2 的 Lys48 和 Arg55 发生突变时，两个 CheR 都不能维持上述互补功能，这表明它们在识别甲基接受趋化蛋白方面与大肠杆菌相似的关键作用。通过微阵列分析表明，问号钩端螺旋体在 Ellinghausen-McCullough-Johnson-Harris 培养基中 28°C 培养时，cheR1 的表达水平明显低于所有其他基因的平均转录水平，而 cheR2 的转录水平明显高于 cheR1，与实时逆转录聚合酶链反应测定结果一致。相同培养物的蛋白质组串联 MS-MS 数据挖掘检测到 16 个来自 CheR2 的肽，但没有来自 CheR1 的肽。因此，尽管这两个基因在大肠杆菌中都具有功能，但结构上更保守的 CheR2 而不是 CheR1 可能是我们实验室培养条件下问号钩端螺旋体趋化适应系统的主要功能成分。
