Cutting S, Anderson M, Lysenko E, Page A, Tomoyasu T, Tatematsu K, Tatsuta T, Kroos L, Ogura T
School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, United Kingdom.
J Bacteriol. 1997 Sep;179(17):5534-42. doi: 10.1128/jb.179.17.5534-5542.1997.
The spoVM gene encodes a 26-amino-acid polypeptide that is essential for spore formation in Bacillus subtilis. A transposon insertion within the spoVM open reading frame has been shown to encode a chimeric protein which is biologically inactive and produces a phenotype identical to that of a deletion and insertion mutation. A genetic approach was used to identify possible interacting proteins, and the membrane-bound FtsH protease was identified. Mutations in ftsH suppressed the sporulation defect of certain spoVM mutants but not others. However, production of the mother cell sigma factors, sigmaE and sigmaK, was abnormal in the suppressed strains, and mutations in either spoVM or ftsH alone impaired sigma factor production and sporulation gene expression. Using FtsH purified from Escherichia coli, we demonstrated that in vitro (i) SpoVM inhibits FtsH protease activity and (ii) SpoVM is a substrate for the FtsH protease. We propose that during sporulation, SpoVM serves as a competitive inhibitor of FtsH activity. This interaction appears to be important for completion of the prespore engulfment step of sporulation, based on the phenotype of certain spoVM ftsH double mutants.
spoVM基因编码一种26个氨基酸的多肽，该多肽对枯草芽孢杆菌的孢子形成至关重要。已证明spoVM开放阅读框内的转座子插入编码一种嵌合蛋白，该蛋白无生物学活性，产生的表型与缺失和插入突变相同。采用遗传学方法鉴定可能相互作用的蛋白，鉴定出了膜结合的FtsH蛋白酶。ftsH中的突变抑制了某些spoVM突变体的孢子形成缺陷，但对其他突变体无效。然而，在受抑制的菌株中，母细胞σ因子sigmaE和sigmaK的产生异常，单独的spoVM或ftsH突变都会损害σ因子的产生和孢子形成基因的表达。使用从大肠杆菌中纯化的FtsH，我们证明在体外（i）SpoVM抑制FtsH蛋白酶活性，（ii）SpoVM是FtsH蛋白酶的底物。我们提出，在孢子形成过程中，SpoVM作为FtsH活性的竞争性抑制剂。基于某些spoVM ftsH双突变体的表型，这种相互作用似乎对孢子形成的前孢子吞噬步骤的完成很重要。
