Distinct requirements for translocation of the N-tail and C-tail of the Escherichia coli inner membrane protein CyoA.
Inner membrane proteins (IMPs) of Escherichia coli use different pathways for membrane targeting and integration. YidC plays an essential but poorly defined role in the integration and folding of IMPs both in conjunction with the Sec translocon and as a Sec-independent insertase. Depletion of YidC only marginally affects the insertion of Sec-dependent IMPs, whereas it blocks the insertion of a subset of Sec-independent IMPs. Substrates of this latter "YidC-only" pathway include the relatively small IMPs M13 procoat, Pf3 coat protein, and subunit c of the F(1)F(0) ATPase. Recently, it has been shown that the steady state level of the larger and more complex CyoA subunit of the cytochrome o oxidase is also severely affected upon depletion of YidC. In the present study we have analyzed the biogenesis of the integral lipoprotein CyoA. Collectively, our data suggest that the first transmembrane segment of CyoA rather than the signal sequence recruits the signal recognition particle for membrane targeting. Membrane integration and assembly appear to occur in two distinct sequential steps. YidC is sufficient to catalyze insertion of the N-terminal domain consisting of the signal sequence, transmembrane segment 1, and the small periplasmic domain in between. Translocation of the large C-terminal periplasmic domain requires the Sec translocon and SecA, suggesting that for this particular IMP the Sec translocon might operate downstream of YidC.
Department of Molecular Microbiology, Institute of Molecular Cell Biology, Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands.
Edwin
E
van Bloois
Gert-Jan
GJ
Haan
Jan-Willem
JW
de Gier
Bauke
B
Oudega
Joen
J
Luirink
D015153:Blotting, Western; D002254:Carbonates / Q000737:chemistry / Q000494:pharmacology; D002384:Catalysis; D002462:Cell Membrane / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D019286:Endopeptidase K / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000502:physiology*; D008074:Lipoproteins / Q000737:chemistry; D026901:Membrane Transport Proteins / Q000737:chemistry*; D008954:Models, Biological; D010957:Plasmids / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D006180:Proton-Translocating ATPases / Q000737:chemistry; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D018271:Signal Recognition Particle
D002254:Carbonates; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D026901:Membrane Transport Proteins; D012346:RNA, Transfer, Amino Acyl; D018271:Signal Recognition Particle; C412443:YIDC protein, E coli; C005686:sodium carbonate; C510605:CyoA protein, E coli; C038862:cytochrome o oxidase; D003576:Electron Transport Complex IV; D019286:Endopeptidase K; D006180:Proton-Translocating ATPases