Kloda A, Martinac B
Department of Pharmacology, QEII Medical Center, The University of Western Australia, Nedlands WA 6907, Australia.
Biophys J. 2001 Jan;80(1):229-40. doi: 10.1016/S0006-3495(01)76009-2.
The TM1 domain of the large conductance mechanosensitive (MS) channel of Escherichia coli was used as a genetic probe to search the genomic database of the archaeon Methanoccoccus jannashii for MscL homologs. We report that the hypothetical protein MJ0170 of M. jannashii exhibited 38.5% sequence identity with the TM1 domain of Eco-MscL. Moreover, MJ0170 was found to be a conserved homolog of MscS, the second type of E. coli MS channel encoded by the yggB gene. Furthermore, we identified a cluster of charged residues KIKEE in the C-terminus of MJ0170 that strikingly resembled the charged C-terminal amino acid cluster present in Eco-MscL (RKKEE). We cloned and expressed MJ0170 in E. coli, which when reconstituted into liposomes or expressed in the cell membrane of giant E. coli spheroplasts, exhibited similar activity to the bacterial MS channels. Our study suggests that the M. jannashii MS channel and its homologs evolved as a result of gene duplication of the ancestral MscL-like molecule with the TM1 domain remaining the most conserved structural motif among prokaryotic MS channels.
大肠杆菌大电导机械敏感（MS）通道的TM1结构域被用作遗传探针，在詹氏甲烷球菌的基因组数据库中搜索MscL同源物。我们报告称，詹氏甲烷球菌的假定蛋白MJ0170与大肠杆菌MscL的TM1结构域具有38.5%的序列同一性。此外，发现MJ0170是由yggB基因编码的大肠杆菌第二种MS通道MscS的保守同源物。此外，我们在MJ0170的C末端鉴定出一组带电荷的残基KIKEE，其与大肠杆菌MscL（RKKEE）中存在的带电荷的C末端氨基酸簇惊人地相似。我们在大肠杆菌中克隆并表达了MJ0170，当将其重组到脂质体中或在巨大的大肠杆菌原生质球细胞膜中表达时，其表现出与细菌MS通道相似的活性。我们的研究表明，詹氏甲烷球菌MS通道及其同源物是由祖先MscL样分子的基因复制进化而来的，其中TM1结构域是原核MS通道中最保守的结构基序。
