Molecular identification of a mechanosensitive channel in archaea.
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.
Kloda
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A
Department of Pharmacology, QEII Medical Center, The University of Western Australia, Nedlands WA 6907, Australia.
Martinac
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B
D000595:Amino Acid Sequence; D001105:Archaea / Q000235:genetics* / Q000502:physiology; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D055592:Biophysical Phenomena; D001703:Biophysics; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D029968:Escherichia coli Proteins; D019143:Evolution, Molecular; D007473:Ion Channels / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D017017:Methanococcus / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D019843:Archaeal Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D007473:Ion Channels; C086596:MscL protein, E coli; D011994:Recombinant Proteins