Different pathways for protein degradation by the FtsH/HflKC membrane-embedded protease complex: An implication from the interference by a mutant form of a new substrate protein, YccA
Different pathways for protein degradation by the FtsH/HflKC membrane-embedded protease complex: An implication from the interference by a mutant form of a new substrate protein, YccA
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DOI：
10.1006/jmbi.1998.1781
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发表时间：
1998-05-29
影响因子：
5.6
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）是一种膜结合和atp依赖的锌金属蛋白酶，它与一对质周暴露的膜蛋白HflK和HflC形成复合物。它是一种蛋白酶，可以降解蛋白质转位酶的非复杂形式的SecY亚基。在这里，我们在大肠杆菌染色体上发现了一类新的secy稳定突变。突变（yccA11）是一个基因（yccA）的内部缺失，该基因被称为疏水蛋白的开放阅读框，具有七个跨膜片段。YccA蛋白在体内和体外均以依赖于ftsh的方式被降解，而YccA11突变蛋白在胞质氨基末端缺乏8个氨基酸残基，因此难以被降解。yccA11突变在过表达时表现出部分显性。交联共免疫沉淀和组氨酸标记实验表明，YccA11和YccA可以结合FtsH和HflKC蛋白。因此，突变体YccA蛋白似乎与SecY竞争，以获得FtsH蛋白水解系统的识别，并且YccA突变所删除的残基是启动FtsH蛋白水解所必需的。有趣的是，YccA11的抑制作用是由HflKC介导的，因为hflK-hflC的缺失抑制了YccA11的表型。yccA11突变也稳定了质子atp酶F-0片段的a亚基，但不稳定噬菌体lambda的CII蛋白或sigma（32）蛋白。根据这些结果，我们认为ftsh依赖性蛋白降解至少有两种途径，其中只有一种（可能是膜蛋白）受到YccA11突变底物的hflkc依赖性干扰。(C) 1998学术出版社有限公司
Escherichia coli FtsH (HflB) is a membrane-bound and ATP-dependent zinc-metalloproteinase, which forms a complex with a pair of periplasmically exposed membrane proteins, HflK and HflC. It is the protease that degrades uncomplexed forms of the SecY subunit of protein translocase. Here,we characterized a new class of SecY-stabilizing mutation on the E. coli chromosome. The mutation (yccA11) is an internal deletion within a gene (yccA) known as an open reading frame for a hydrophobic protein with putative seven transmembrane segments. The YccA protein was found to be degraded in an FtsH-dependent manner in vivo and in vitro, whereas the YccA11 mutant protein, lacking eight amino acid residues within the amino-terminal cytoplasmic domain, was refractory to the degradation. The yccA11 mutation exhibited partial dominance when overexpressed. Cross-linking co-immunoprecipitation, and histidine tagging experiments showed that YccA11 as well as YccA can associate with both the FtsH and the HflKC proteins. Thus, the mutant YccA protein appeared to compete with SecY for recognition by the FtsH proteolytic system and the residues deleted by the yccA mutation are required for the initiation of proteolysis by FtsH. Interestingly, the inhibitory action of YccA11 was mediated by HflKC, since the deletion of hflK-hflC suppressed the yccA11 phenotype. The yccA11 mutation stabilized subunit a of the proton ATPase F-0 segment as well, but not the CII protein of bacteriophage lambda or the sigma(32) protein. From these results we suggest that there are at least two pathways for FtsH-deyendent protein degradation, only one of which (probably for membrane proteins) is subject to the HflKC-dependent interference by the YccA11 mutant substrate. (C) 1998 Academic Press Limited.