A protease complex in the Escherichia coli plasma membrane: HflKC (HflA) forms a complex with FtsH (HflB), regulating its proteolytic activity against SecY
A protease complex in the Escherichia coli plasma membrane: HflKC (HflA) forms a complex with FtsH (HflB), regulating its proteolytic activity against SecY
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DOI：
10.1002/j.1460-2075.1996.tb01000.x
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发表时间：
1996-11-15
期刊：
影响因子：
11.4
通讯作者：
Ito, K
中科院分区：
文献类型：
--
作者：
Kihara, A;Akiyama, Y;Ito, K
大肠杆菌FtsH（HflB），一种膜结合的ATP酶，是蛋白质转位酶SecY亚基的未复合形式的蛋白水解降解所需的。我们现在已经分离了在HflK-HflC膜蛋白复合物中引起氨基酸取代的SecY稳定突变。尽管HflKC蛋白被认为具有针对λ cII蛋白的蛋白水解活性，但hflK-HflC的缺失并不稳定SecY。相反，突变等位基因是部分显性的，并且ftsH的过表达抑制了突变效应，这表明突变蛋白拮抗SecY的降解。这些结果提高了甚至野生型HflKC蛋白也拮抗FtsH的可能性。与该观点一致，hflKC无效突变加速了SecY 24蛋白的降解。此外，交联，免疫共沉淀，组氨酸标记实验和凝胶过滤实验均表明FtsH与HflKC在体内外形成复合物，纯化的HflKC蛋白在体外抑制FtsH蛋白的SecY降解活性，表明FtsH蛋白的蛋白水解活性受HflKC的结合负调控。
Escherichia coli FtsH (HflB), a membrane-bound ATPase is required for proteolytic degradation of uncomplexed forms of the protein translocase SecY subunit, We have now isolated SecY-stabilizing mutations that cause an amino acid substitution in the HflK-HflC membrane protein complex, Although HflKC protein was believed to have a proteolytic activity against lambda cII protein, deletion of hflK-hflC did not stabilize SecY, Instead, the mutant alleles were partially dominant and overexpression of ftsH suppressed the mutational effects, suggesting that the mutant proteins antagonized the degradation of SecY, These results raise the possibility that even the wildtype HflKC protein acts to antagonize FtsH, Consistent with this notion, the hflkC null mutation accelerated degradation of the SecY24 protein, Furthermore crosslinking, co-immunoprecipitation, histidine-tagging and gel filtration experiments all indicated that FtsH and HflKC form a complex in vivo and in vitro, Finally, purified HflKC protein inhibited the SecY-degrading activity of purified FtsH protein in vitro, These results indicate that the proteolytic activity of FtsH is modulated negatively by its association with HflKC.