Crawford E W, Shimkets L J
Department of Microbiology, University of Georgia, Athens 30602-2605, USA.
Mol Microbiol. 2000 Aug;37(4):788-99. doi: 10.1046/j.1365-2958.2000.02039.x.
Disruption of the Myxococcus xanthus socE gene bypasses the requirement for the cell contact-dependent C-signalling system mediated by CsgA and restores fruiting body morphogenesis and spore differentiation. The socE gene has been identified by genetic complementation, cloned and sequenced. SocE is highly basic, unique and is predicted to be a soluble protein with a molecular size of 53. 6 kDa. The socE and csgA genes have opposite transcription patterns during the M. xanthus life cycle. socE expression is high in growing cells and declines during the early stages of development. Expression of csgA is low in vegetative cells and increases during development. socE transcription is negatively regulated by the stringent response, the major amino acid-sensing pathway in M. xanthus. A relA null mutation, which eliminates the stringent response, prevents the decline in socE expression normally observed at the onset of development. CsgA is positively regulated by the stringent response and is negatively regulated by socE. A relA mutation virtually eliminates developmental csgA expression. Expression of socE in Escherichia coli leads to a rapid loss of viability in relA- cells during stationary phase, suggesting a relationship with the stringent response.
黄色黏球菌socE基因的破坏绕过了由CsgA介导的细胞接触依赖性C信号系统的需求，并恢复了子实体形态发生和孢子分化。通过遗传互补鉴定了socE基因，进行了克隆和测序。SocE具有高度碱性，是独特的，预计是一种分子大小为53.6 kDa的可溶性蛋白质。在黄色黏球菌的生命周期中，socE和csgA基因具有相反的转录模式。socE在生长细胞中表达高，在发育早期下降。csgA在营养细胞中表达低，在发育过程中增加。socE转录受严谨反应负调控，严谨反应是黄色黏球菌主要的氨基酸感应途径。relA无效突变消除了严谨反应，阻止了通常在发育开始时观察到的socE表达下降。CsgA受严谨反应正调控，受socE负调控。relA突变实际上消除了发育过程中csgA的表达。在大肠杆菌中socE的表达导致relA-细胞在稳定期活力迅速丧失，表明与严谨反应有关。
