The two membrane segments of leader peptidase partition one by one into the lipid bilayer via a Sec/YidC interface |
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Authors: | Houben Edith N G ten Hagen-Jongman Corinne M Brunner Josef Oudega Bauke Luirink Joen |
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Institution: | Department of Molecular Microbiology, Institute of Molecular Cell Biology, Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands. |
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Abstract: | We have addressed the mechanism of insertion of both transmembrane segments (TMs) of leader peptidase, a double-spanning protein, into the Escherichia coli inner membrane. Using photo-crosslinking, the first TM (H1) was shown to insert at a Sec-translocon/YidC interface in a fixed orientation. H1 lost its contacts with the Sec-translocon and gained access to lipids near YidC soon after complete exposure outside the ribosome. Following lipid integration, it moved away from the Sec/YidC insertion site. The second TM (H2) inserted and interacted with SecY and YidC in a similar transient fashion. The data are consistent with a linear integration model in which the TMs of polytopic inner membrane proteins move one by one from a Sec/YidC insertion site into the lipid bilayer. We propose that YidC assists the lipid partitioning of single TMs. |
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