Distinct Requirements for Translocation of the N-tail and C-tail of the Escherichia coli Inner Membrane Protein CyoA

Abstract

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 F1F0 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. 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 F1F0 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. In Escherichia coli, IMPs 4The abbreviations used are: IMP, inner membrane protein; Ffh, Fifty-four homologue; SRP, signal recognition particle; TF, trigger factor; TM, transmembrane segment; SPaseII, signal peptidase II; HA, hemagglutinin. are targeted and inserted into the inner membrane via different pathways (1Gier J.W. Annu. Rev. Microbiol. 2005; 59: 329-355Crossref PubMed Scopus (157) Google Scholar). Targeting of most IMPs analyzed until now depends on a conserved system consisting of the signal recognition particle (SRP) and its receptor FtsY (2Luirink J. Sinning I. Biochim. Biophys. Acta. 2004; 1694: 17-35PubMed Google Scholar, 3Koch H.G. Moser M. Muller M. Rev. Physiol. Biochem. Pharmacol. 2003; 146: 55-94Crossref PubMed Google Scholar). The E. coli SRP, which consists of a signal sequence binding protein (Ffh for Fifty-four homologue) and a 4.5 S RNA, samples nascent chains at the ribosomal exit site for the presence of particularly hydrophobic targeting signals that are primarily present in nascent IMPs. The ribosome nascent chain-SRP complex is transferred to the Sec translocon located in the inner membrane by the SRP receptor FtsY that is located both in the cytoplasm and inner membrane. The mechanism of transfer by FtsY is not well understood but most likely involves interaction of FtsY with membrane lipids and with the Sec translocon component SecY (4Angelini S. Deitermann S. Koch H.G. EMBO Rep. 2005; 6: 476-481Crossref PubMed Scopus (109) Google Scholar). GTP binding and hydrolysis by Ffh and FtsY regulates the vectorial transfer process and recycling of the components involved (5Shan S.O. Walter P. FEBS Lett. 2005; 579: 921-926Crossref PubMed Scopus (108) Google Scholar). The heterotrimeric core of the Sec translocon comprises the integral membrane components SecY, SecE, and SecG. It functions in membrane insertion of most IMPs and in translocation of secretory proteins (6Veenendaal A.K. van der Does C. Driessen A.J. Biochim. Biophys. Acta. 2004; 1694: 81-95Crossref PubMed Scopus (102) Google Scholar). The peripheral ATPase SecA is dynamically associated with the cytoplasmic side of the SecYEG core and drives the translocation of secretory proteins and large periplasmic domains of IMPs (7Vrontou E. Economou A. Biochim. Biophys. Acta. 2004; 1694: 67-80Crossref PubMed Scopus (103) Google Scholar). YidC has been identified as a novel Sec-associated component by cross-link and pull-down experiments and plays a role in the biogenesis of IMPs (8Yi L. Dalbey R.E. Mol. Memb. Biol. 2005; 22: 101-111Crossref PubMed Scopus (57) Google Scholar). In vivo depletion of YidC (which is an essential protein) generally does not affect protein translocation and only slightly affects the insertion of Sec-dependent IMPs into the membrane (9Urbanus M.L. Scotti P.A. Froderberg L. Saaf A. deGier J.W.L. Brunner J. Samuelson J.C. Dalbey R.E. Oudega B. Luirink J. EMBO Rep. 2001; 2: 524-529Crossref PubMed Scopus (154) Google Scholar, 10Froderberg L. Houben E. Samuelson J.C. Chen M. Park S.K. Phillips G.J. Dalbey R. Luirink J. de Gier J.W. Mol. Microbiol. 2003; 47: 1015-1027Crossref PubMed Scopus (70) Google Scholar). The function of Sec-associated YidC has been investigated for only a limited number of IMPs and is currently not well understood. Available evidence suggests that it acts downstream of the Sec translocon to facilitate the lateral transfer and assembly of TMs and to assist the folding of polytopic IMPs (9Urbanus M.L. Scotti P.A. Froderberg L. Saaf A. deGier J.W.L. Brunner J. Samuelson J.C. Dalbey R.E. Oudega B. Luirink J. EMBO Rep. 2001; 2: 524-529Crossref PubMed Scopus (154) Google Scholar, 11Houben E.N. ten Hagen-Jongman C.M. Brunner J. Oudega B. Luirink J. EMBO Rep. 2004; 5: 970-975Crossref PubMed Scopus (39) Google Scholar, 12Beck K. Eisner G. Trescher D. Dalbey R.E. Brunner J. Muller M. EMBO Rep. 2001; 2: 709-714Crossref PubMed Scopus (138) Google Scholar, 13Nagamori S. Smirnova I.N. Kaback H.R. J. Cell Biol. 2004; 165: 53-62Crossref PubMed Scopus (161) Google Scholar). On the other hand, TMs in Sec-dependent nascent IMPs contact YidC very early in biogenesis, suggesting an additional role in the reception and recognition of TMs in the context of the Sec translocon (14Houben E.N.G. Urbanus M.L. van der M. ten Hagen-Jongman C.M. Driessen Brunner J. Oudega B. Luirink J. J. Biol. PubMed Scopus Google Scholar, E.N. R. Oudega B. Luirink J. J. Cell Biol. 2005; PubMed Scopus Google Scholar). The of YidC is by the that it also functions of the Sec translocon J. G. G. L. D. Dalbey R. A. EMBO J. 2004; PubMed Scopus Google Scholar, M. M. S. Luirink J. J. Biol. 2005; PubMed Scopus Google Scholar). Depletion of YidC membrane insertion of the Sec-independent small Pf3 and M13 coat proteins that to into the membrane J.C. Chen I. M. A. Phillips G.J. Dalbey R.E. PubMed Scopus Google Scholar). In have shown that YidC is not only but also sufficient for membrane insertion of Pf3 coat protein the translocation of its small N-terminal domain J. G. G. L. D. Dalbey R. A. EMBO J. 2004; PubMed Scopus Google Scholar). It is as not this Sec-independent function of YidC is also in a of a of YidC the Sec study has shown that the of YidC to in the assembly of cytochrome o oxidase and the complex der M. Urbanus M.L. ten Hagen-Jongman C.M. Oudega B. Driessen Luirink J. S. A. 2003; Scopus Google Scholar). the of c of the and CyoA of the cytochrome o upon the depletion of YidC of the on the insertion of small coat YidC is to the that membrane insertion of the IMPs and that in to and CyoA. it has been that YidC plays a role in the membrane insertion of and CyoA der M. Urbanus M.L. ten Hagen-Jongman C.M. Oudega B. Driessen Luirink J. S. A. 2003; Scopus Google Scholar). that but not the SecYEG is for membrane insertion of a IMP with very periplasmic at the and E. G. de Gier J.W. Oudega B. Luirink J. FEBS Lett. 2004; PubMed Scopus Google Scholar, der M. P. S. Driessen A.J. J. Cell Biol. 2004; 165: PubMed Scopus Google Scholar, L. Chen M. Dalbey R.E. J. Biol. 2004; PubMed Scopus Google Scholar). In to CyoA is a lipoprotein that is with a signal sequence a conserved sequence that the signal peptidase site J. A. PubMed Scopus Google Scholar). CyoA has two but the is by a large In the present study we have analyzed the targeting and insertion of CyoA in vivo experiments and an in Collectively, our data that the SRP with the first of CyoA than with its signal to targeting of CyoA to the insertion site in the inner membrane. Membrane insertion to in two distinct YidC is and sufficient for membrane assembly of the N-terminal of the protein, whereas translocation of the large C-terminal periplasmic domain requires the Sec suggests that for membrane assembly of the Sec translocon downstream of YidC. and and and protein and other by The our Ffh, and SecY have been our E. G. de Gier J.W. Oudega B. Luirink J. FEBS Lett. 2004; PubMed Scopus Google Scholar, P.A. Urbanus M.L. Brunner J. de Gier J.W. G. van der Does C. Driessen A.J. Oudega B. Luirink J. EMBO J. PubMed Scopus Google Scholar). and coli used to a for of in and of in the presence of used for the of membrane used as for The 4.5 S depletion the depletion and the YidC depletion as L. Houben E. Samuelson J.C. Chen M. Park S.K. Phillips G.J. Dalbey R. Luirink J. de Gier J.W. Mol. Microbiol. 2003; 47: 1015-1027Crossref PubMed Scopus (70) Google Scholar). The YidC depletion and its as L. Houben E.N. L. Luirink J. de Gier J.W. J. Biol. 2004; PubMed Scopus Google Scholar). The Ffh depletion which a and its as S. A. 2001; PubMed Scopus Google Scholar, J. J. PubMed Scopus Google Scholar). The and its K. K. EMBO J. PubMed Scopus Google in at SecY, and to early at in the in to the in vivo the E. coli an by a at the of CyoA. The into P.A. Urbanus M.L. Brunner J. de Gier J.W. G. van der Does C. Driessen A.J. Oudega B. Luirink J. EMBO J. PubMed Scopus Google into L. C. Mol. Microbiol. PubMed Scopus Google and into to in of different The the protein, by as the a CyoA in a as comprises to a C-terminal by the and a in cross-link the and by as P.A. Urbanus M.L. Brunner J. de Gier J.W. G. van der Does C. Driessen A.J. Oudega B. Luirink J. EMBO J. PubMed Scopus Google as The a CyoA of and a C-terminal to the the CyoA an at to of a as P.A. Urbanus M.L. Brunner J. de Gier J.W. G. van der Does C. Driessen A.J. Oudega B. Luirink J. EMBO J. PubMed Scopus Google Scholar). The sequence of by for in Membrane and to early of and for by and of and for by with and to as L. Houben E. Samuelson J.C. Chen M. Park S.K. Phillips G.J. Dalbey R. Luirink J. de Gier J.W. Mol. Microbiol. 2003; 47: 1015-1027Crossref PubMed Scopus (70) Google Scholar). of the with for on to the to K. proteins and with the P.A. Urbanus M.L. Brunner J. de Gier J.W. G. van der Does C. Driessen A.J. Oudega B. Luirink J. EMBO J. PubMed Scopus Google Scholar). analyzed by and proteins by the to SecA of of to of and in of for to CyoA with to as L. Houben E. Samuelson J.C. Chen M. Park S.K. Phillips G.J. Dalbey R. Luirink J. de Gier J.W. Mol. Microbiol. 2003; 47: 1015-1027Crossref PubMed Scopus (70) Google and with on for and at The in and with P.A. Urbanus M.L. Brunner J. de Gier J.W. G. van der Does C. Driessen A.J. Oudega B. Luirink J. EMBO J. PubMed Scopus Google Scholar). The in and analyzed by and proteins by In as P.A. Urbanus M.L. Brunner J. de Gier J.W. G. van der Does C. Driessen A.J. Oudega B. Luirink J. EMBO J. PubMed Scopus Google into CyoA nascent chains by of an in an E. coli in system to the nascent Targeting to membrane and as P.A. Urbanus M.L. Brunner J. de Gier J.W. G. van der Does C. Driessen A.J. Oudega B. Luirink J. EMBO J. PubMed Scopus Google Scholar). and analyzed by and by as P.A. Urbanus M.L. Brunner J. de Gier J.W. G. van der Does C. Driessen A.J. Oudega B. Luirink J. EMBO J. PubMed Scopus Google Scholar). and of the present study we have investigated the targeting and membrane integration of CyoA. in the by a to the of the protein first that of the does not with the complex and of CyoA. a pathway by of a conserved that the N-terminal of the protein S. J. 22: PubMed Scopus Google Scholar). The are with at the of the the and the by SPaseII, and with at the of the only and by the to the of CyoA in the presence of and CyoA the samples CyoA the shown in of both and CyoA is by that is and by SPaseII, CyoA. the CyoA slightly than CyoA in data that of an to the of CyoA does not with its and with a study two other L. Houben E.N. L. Luirink J. de Gier J.W. J. Biol. 2004; PubMed Scopus Google Scholar). CyoA by the SRP to the Inner IMPs that have signal the SRP for targeting. the role of the SRP in targeting of which is with a signal sequence, we used a to membrane assembly of in in which the of both components of the SRP, Ffh and the 4.5 S RNA, of in which is of an in the presence of to and with to protein shown in in the presence of Ffh only in that the is and to K. the does not with membrane assembly of our and are cytoplasmic and membrane proteins used to and the of Depletion of Ffh in of suggesting that the SRP is for targeting of CyoA to the inner membrane. Translocation and of the Sec-dependent protein not affected that of the Sec translocon not of a small of upon depletion of Ffh has been E. G. de Gier J.W. Oudega B. Luirink J. FEBS Lett. 2004; PubMed Scopus Google Scholar, E. S. G. M. Oudega B. Kaback H.R. Luirink J. J. Biol. 2005; PubMed Scopus Google and to Depletion of Ffh by the Ffh in a by CyoA targeting also analyzed in the relatively and J. J. PubMed Scopus Google of the data in for the of the and that the in of the with of the not affected as for this role for the SRP in CyoA targeting investigated in the 4.5 S depletion In with the of depletion of Ffh, depletion of 4.5 S also in not the suggest that CyoA requires the SRP for membrane targeting. The SecYEG and SecA for Translocation of the C-terminal of for membrane assembly of CyoA that are for the of of the Sec translocon and YidC the the role of the Sec we used the SecY its and the depletion in which the essential is of an of SecY depletion of in the of the core of the shown in of SecY a on the of CyoA K. of CyoA that the C-terminal is and the is by K. upon of SecY, CyoA to a large into a that slightly than CyoA. to this CyoA with an and a N-terminal of CyoA affected that signal sequence and to not a with the well role of the Sec in the transfer of the inner membrane (6Veenendaal A.K. van der Does C. Driessen A.J. Biochim. Biophys. Acta. 2004; 1694: 81-95Crossref PubMed Scopus (102) Google Scholar). suggest that the small N-terminal domain of CyoA of does not the Sec translocon to the periplasmic side of the in to the large C-terminal that the to of the core of the the assembly of CyoA also analyzed in the depletion Depletion of a on the translocation of the CyoA domains as of SecY not The ATPase SecA is to the translocation of large periplasmic domains of IMPs the SecYEG translocon (1Gier J.W. Annu. Rev. Microbiol. 2005; 59: 329-355Crossref PubMed Scopus (157) Google Scholar). SecA is involved in transfer of the large C-terminal domain of a in the presence of to SecA function In the of of of the In the presence of the as upon of SecY depletion of SecE, that SecA is to catalyze membrane transfer of the C-terminal translocation of the N-terminal and signal sequence not affected by of SecA function by by a and translocation of the suggest that the Sec translocon and SecA in to the CyoA whereas translocation of the requires the Sec translocon YidC for Translocation and Membrane of the CyoA the role of YidC in the membrane assembly of we used the YidC depletion in which the is of an In the presence of the the inner membrane and by K. Depletion of YidC in of and of CyoA. a the translocation and of and suggesting that of the Sec translocon not with of Sec translocon components not YidC depletion by the YidC in a by YidC study the of the CyoA upon depletion of and not for YidC to which integral membrane proteins peripheral membrane proteins and CyoA in the in the presence of of an integral membrane not depletion of the CyoA in the not suggesting that YidC is not for the membrane insertion of CyoA. The data that YidC is for translocation of the N-terminal and signal sequence In the of the C-terminal domain is also of which is to an vectorial assembly to Translocation of the of CyoA Does the Sec data that membrane insertion and translocation of the and of CyoA different the for translocation of the CyoA we a CyoA that and the large C-terminal The an at the to by a of to of the to the of IMPs are at the cytoplasmic of the inner membrane and to the of IMPs by translocation of domains (1Gier J.W. Annu. Rev. Microbiol. 2005; 59: 329-355Crossref PubMed Scopus (157) Google Scholar). and of this a In a the is and at the by that the is and has its The is in that this is not but is in an in of the of that the is and by and to the the of the is by in a slightly In experiments we investigated the for membrane assembly of the of the Sec translocon in the depletion depletion of on the of depletion of by the and translocation of the SecY and its not YidC the YidC and its Depletion of YidC of in of the that to by K. the of the is to the and translocation of that of the Sec translocon not Depletion of YidC by the YidC in a by the in vivo that the of CyoA the in a Sec-independent CyoA with Ffh, SecY, SecE, and in vivo experiments that targeting and membrane assembly of the CyoA protein requires the SRP, the SecYEG and the of we used a in to the of nascent CyoA that are targeting and membrane we analyzed the of biogenesis of CyoA. is more hydrophobic than the signal sequence more likely to a role in membrane targeting de Gier G. ten Hagen-Jongman C.M. Oudega B. Luirink J. Mol. Microbiol. PubMed Scopus Google Scholar). chains of CyoA in an E. coli to a of and by the of that the ribosome the signal sequence and first are well of the ribosome at this nascent The CyoA a at in the that in by the of a that a with a to of in nascent CyoA. that the by the in nascent CyoA of the in the of membrane and to the and of the CyoA in the E. coli of that suggests of with the SRP, with the in vivo SRP data the of membrane membrane membrane insertion of nascent CyoA. by and of the nascent chains by of and in which YidC and SecY identified as by and a at to that of nascent CyoA is primarily in contact with YidC and SecY at this membrane the signal sequence, in which the signal sequence a in the core is to the to and the ribosomal protein to Ffh membrane components not are with the relatively of the signal sequence and cross-link data other signal of E.N. R. Oudega B. Luirink J. J. Cell Biol. 2005; PubMed Scopus Google Scholar, de Gier G. ten Hagen-Jongman C.M. Oudega B. Luirink J. Mol. Microbiol. PubMed Scopus Google Scholar). the cross-link data that recruits the SRP for targeting of nascent CyoA and into the membrane at the insertase. CyoA is of the integral membrane of the cytochrome o oxidase complex in the E. coli inner membrane. CyoA is an polytopic IMP in the that it is with an lipoprotein signal sequence that is the protein J. A. PubMed Scopus Google Scholar). CyoA with two hydrophobic TMs and an N-terminal that is to the inner membrane via It has been shown most other polytopic IMPs, the level of CyoA in the inner membrane upon depletion of suggesting an role of YidC in the biogenesis of CyoA der M. Urbanus M.L. ten Hagen-Jongman C.M. Oudega B. Driessen Luirink J. S. A. 2003; Scopus Google Scholar). in this suggests that YidC is and sufficient for assembly of the N-terminal its role in the assembly of the CyoA that in a vectorial In a is that the targeting and membrane assembly of CyoA on the in vivo and in experiments in this The SRP nascent CyoA via to the insertion site in the membrane by the that CyoA in the in SRP an membrane protein that is targeted via the is The in cross-link experiments suggest that targeting is not until is at the ribosomal nascent exit site and with The signal sequence the ribosome in nascent chains does not contact the SRP into the membrane. at this the signal sequence is to the trigger and the ribosomal protein The of a complex that trigger to the nascent exit the exit a L. B. E. 2004; PubMed Scopus Google Scholar). contact of nascent CyoA with the of rather than the signal sequence by the SRP is by the more hydrophobic core of that is the level for SRP binding in to the hydrophobic core of the signal sequence this and SRP the signal sequence and to facilitate the of a that is for the membrane integration at YidC of the signal sequence, and periplasmic domain that the The SRP is to the CyoA complex to but of this and a of the SRP receptor FtsY in a interaction SRP, and the YidC has been M. R. J. Cell Biol. 2003; PubMed Scopus Google Scholar). It that of the SRP in targeting of IMP that requires YidC for membrane is E. G. de Gier J.W. Oudega B. Luirink J. FEBS Lett. 2004; PubMed Scopus Google Scholar, der M. P. S. Driessen A.J. J. Cell Biol. 2004; 165: PubMed Scopus Google Scholar, L. Chen M. Dalbey R.E. J. Biol. 2004; PubMed Scopus Google Scholar). Targeting of membrane proteins via the hydrophobic sequence is not on the insertion of M13 procoat, the transmembrane and the a role for the more hydrophobic sequence in targeting and of membrane insertion J. A. PubMed Scopus Google Scholar, A. K. A. J. Biol. PubMed Scopus Google Scholar, L. J. A. C. PubMed Scopus (57) Google Scholar). not for targeting is the role for the CyoA signal It to transfer the N-terminal domain in the signal sequence and to the periplasmic side of the membrane in a of to of the CyoA signal sequence of the oxidase in the the of the not J. A. PubMed Scopus Google Scholar). of the conserved N-terminal located at the might to the in the membrane. of this conserved into an and signal sequence but does not affect membrane assembly and of the oxidase J. A. PubMed Scopus Google Scholar). In this the signal sequence functions as an additional TM, the downstream sequence to the membrane in the of Translocation of the periplasmic that in CyoA requires whereas the Sec is the of the oxidase that this is only and J. S. G. A. M. L. A. S. M. Biol. PubMed Scopus Google Scholar). It has been that YidC is and sufficient for translocation of the periplasmic domain in the signal sequence and of M13 M. K. J. L. A. Dalbey R.E. 2005; PubMed Scopus Google Scholar). It shown that translocation of this only Sec-dependent the number of in the of the in is M. K. J. L. A. Dalbey R.E. 2005; PubMed Scopus Google Scholar). YidC is to relatively domains in a signal sequence and a It to investigated this translocation involves a of YidC it is a of of transmembrane of nascent CyoA in which both the signal sequence and have the ribosome that at this is not only to as but also to SecY and SecE, which are only at a in is inserted and the large C-terminal domain is into the the Sec translocon is the YidC in to of CyoA that are in the ribosomal exit the YidC is dynamically with the Sec In this it that is evidence for of Sec-associated and YidC. a of the E. coli SecYEG to a complex has been very an of the translocon in the of a membrane protein K. C. S. J. 2005; PubMed Scopus Google Scholar). The suggests a and of with at the of the by the YidC this side to the transfer of nascent the and the of the Sec the Sec translocon is for translocation of the large periplasmic domain downstream of acts as a signal sequence and in the SecYEG translocon to translocation of the in a is to the assembly and translocation of other large periplasmic domains in IMPs as present in and (1Gier J.W. Annu. Rev. Microbiol. 2005; 59: 329-355Crossref PubMed Scopus (157) Google Scholar). It is YidC at this its transfer into the the Sec translocon into the via and with into the oxidase latter not by and In we have evidence that membrane assembly of CyoA in two distinct sequential steps. the mechanism the data suggest that in this the Sec downstream of the YidC the of CyoA in the inner membrane upon depletion of YidC. It to investigated other membrane proteins this pathway for membrane integration. It is of that the data are to of a IMP that has been used in biogenesis has the as CyoA small N-terminal and large C-terminal periplasmic but is an N-terminal signal is targeted by the SRP that with de Gier G. ten Hagen-Jongman C.M. Oudega B. Luirink J. Mol. Microbiol. PubMed Scopus Google Scholar, Gier J.W.L. P. Phillips G.J. Luirink J. G. FEBS Lett. PubMed Scopus Google Scholar). to translocation of the small N-terminal periplasmic domain does not the Sec in to the large periplasmic domain downstream of A. Dalbey R.E. J. Biol. PubMed Google Scholar). On the other hand, depletion of YidC has on the assembly of L. Houben E. Samuelson J.C. Chen M. Park S.K. Phillips G.J. Dalbey R. Luirink J. de Gier J.W. Mol. Microbiol. 2003; 47: 1015-1027Crossref PubMed Scopus (70) Google that is rather in the use of different in to the insertion of the signal in CyoA and M13 that appear the CyoA in the inner membrane of in distinct for membrane the YidC is for translocation of both the and the inner membrane into the S. Mol. Biol. PubMed Scopus (157) Google Scholar, K. J. E. FEBS Lett. PubMed Scopus Google whereas a YidC is involved in of the C-terminal domain S. Mol. Biol. 2004; PubMed Scopus Google Scholar, Mol. Biol. PubMed Scopus Google Scholar). the that not a Sec the of a insertion mechanism are to ten Hagen-Jongman for and to for and of the and are for and