The mechanosensitive channel protein MscL is targeted by the SRP to the novel YidC membrane insertion pathway of Escherichia coli.
The mechanosensitive channel MscL in the inner membrane of Escherichia coli is a homopentameric complex involved in homeostasis when cells are exposed to hypo-osmotic conditions. The E. coli MscL protein is synthesized as a polypeptide of 136 amino acid residues and uses the bacterial signal recognition particle (SRP) for membrane targeting. The protein is inserted into the membrane independently of the Sec translocon. Mutants affected in the Sec-components are competent for MscL assembly. Translocation of the periplasmic domain was detected using a membrane-impermeant, sulfhydryl-specific gel-shift reagent. The modification of a single cysteine residue at position 68 indicated its translocation across the inner membrane. From these in vivo experiments, it is concluded that the electrical chemical membrane potential is not necessary for membrane insertion of MscL. However, depletion of the membrane insertase YidC inhibits translocation of the protein across the membrane. We show here that YidC is essential for efficient membrane insertion of the MscL protein. YidC is a component of a recently identified membrane insertion pathway that is evolutionarily conserved in bacteria, mitochondria and chloroplasts.
Facey
Sandra J
SJ
Institute of Microbiology, University of Hohenheim, 70599 Stuttgart, Germany.
Neugebauer
Stella A
SA
Krauss
Susanne
S
Kuhn
Andreas
A
D000251:Adenosine Triphosphatases / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D004563:Electrochemistry / Q000379:methods; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D019143:Evolution, Molecular; D007473:Ion Channels / Q000737:chemistry / Q000502:physiology*; D008564:Membrane Potentials; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D021381:Protein Transport; D018892:Proton-Motive Force; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D018271:Signal Recognition Particle
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D007473:Ion Channels; D026901:Membrane Transport Proteins; C086596:MscL protein, E coli; D000069816:SEC Translocation Channels; D018271:Signal Recognition Particle; C412443:YIDC protein, E coli; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins