Ward M J, Harrison D M, Ebner M J, Armitage J P
Department of Biochemistry, Oxford University, UK.
Mol Microbiol. 1995 Oct;18(1):115-21. doi: 10.1111/j.1365-2958.1995.mmi_18010115.x.
Analysis of the DNA sequence directly upstream of the chemotaxis operon of Rhodobacter sphaeroides identified a single gene whose product has strong similarity to the methyl-accepting chemotaxis proteins (MCPs) found in enteric bacteria. The deduced protein had a highly conserved signalling sequence and only one very hydrophobic region at the N-terminus, in contrast to enteric MCPs. A possible cytoplasmic location of the majority of the protein was supported by Western blotting. The mcpA gene was insertionally inactivated and the resulting phenotype examined using swarm plate assays. The mutant lacking McpA lost chemotaxis to a wide range of attractant stimuli but only under aerobic conditions; it retained almost normal chemotaxis under anaerobic/photosynthetic conditions. The identification of a sensory protein which is active only under one set of growth conditions suggests that R. sphaeroides probably has several MCPs, which co-ordinately respond to changes in environmental conditions. Southern hybridization at relaxed stringency to the conserved sequence of the R. sphaeroides and Caulobacter crescentus mcp genes identified three possible additional mcp genes.
对球形红细菌趋化操纵子上游紧邻的DNA序列进行分析，鉴定出一个单一基因，其产物与肠道细菌中发现的甲基接受趋化蛋白（MCPs）具有高度相似性。与肠道MCPs相比，推导的蛋白质具有高度保守的信号序列，且在N端只有一个非常疏水的区域。蛋白质印迹法支持了大部分蛋白质可能定位于细胞质的观点。mcpA基因通过插入失活，并使用群体平板试验检测所得表型。缺乏McpA的突变体在多种引诱剂刺激下失去趋化性，但仅在有氧条件下如此；在厌氧/光合条件下它保留了几乎正常的趋化性。鉴定出一种仅在一组生长条件下具有活性的传感蛋白，这表明球形红细菌可能有几种MCPs，它们协同响应环境条件的变化。以宽松严谨度对球形红细菌和新月柄杆菌mcp基因的保守序列进行Southern杂交，鉴定出另外三个可能的mcp基因。
