Gillen K L, Hughes K T
Department of Microbiology, University of Washington, Seattle 98195.
J Bacteriol. 1991 Oct;173(20):6453-9. doi: 10.1128/jb.173.20.6453-6459.1991.
The expression of flagellin in Salmonella typhimurium is coupled to the assembly of complete flagella. Mutations which disrupt this coupling define a gene, flgM, which represses the expression of the flagellin genes in strains with mutations in the basal body, switch, or hook flagellar gene (K. L. Gillen and K. T. Hughes, J. Bacteriol. 173:2301-2310, 1991). Complementation studies demonstrated that the flgM gene is contained within a 600-bp cloned DNA fragment. Sequence analysis revealed that this fragment carries a small open reading frame corresponding to a 97-amino-acid protein. The FlgM protein observed in a T7-mediated expression system showed an apparent molecular mass of 9.5 kDa, similar to the predicted size of 10.6 kDa. Upstream of the flgM coding region is a putative promoter sequence which shows strong homology to that thought to be recognized by the flagellin-specific sigma factor (FliA). Consistent with the use of this promoter in vivo, promoter mapping by primer extension demonstrated a transcriptional start site 11 bases downstream from the center of the putative -10 promoter element, which was dependent on functional FliA for full expression.
鼠伤寒沙门氏菌中鞭毛蛋白的表达与完整鞭毛的组装相关联。破坏这种关联的突变定义了一个基因flgM，该基因在基体、开关或钩鞭毛基因突变的菌株中抑制鞭毛蛋白基因的表达（K. L. 吉伦和K. T. 休斯，《细菌学杂志》173:2301 - 2310，1991）。互补研究表明flgM基因包含在一个600碱基对的克隆DNA片段中。序列分析显示该片段携带一个小的开放阅读框，对应一个97个氨基酸的蛋白质。在T7介导的表达系统中观察到的FlgM蛋白的表观分子量为9.5 kDa，与预测的10.6 kDa大小相似。flgM编码区上游是一个假定的启动子序列，它与被认为由鞭毛蛋白特异性sigma因子（FliA）识别的启动子序列具有很强的同源性。与该启动子在体内的使用情况一致，通过引物延伸进行的启动子定位表明转录起始位点在假定的 -10启动子元件中心下游11个碱基处，其完全表达依赖于功能性的FliA。
