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Membrane Integrity during the Co‐translational Integration of Multi‐spanning Membrane Proteins
Author(s) -
Johnson Arthur E.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a890
Subject(s) - translocon , endoplasmic reticulum , transmembrane protein , membrane , membrane protein , förster resonance energy transfer , biophysics , microbiology and biotechnology , integral membrane protein , chemistry , biology , biochemistry , fluorescence , physics , receptor , quantum mechanics
Maintaining the permeability barrier of the membrane of the endoplasmic reticulum (ER) is particularly problematic when multi‐spanning membrane proteins are integrated into the bilayer at sites termed translocons. Previous work has demonstrated that ion passage through the aqueous pore in the translocon is regulated by a complex choreography of interactions that involve primarily a ribosome in the cytosol, a translocon in the ER membrane, and BiP, an Hsp70 homolog located in the ER lumen. To identify the mechanisms involved in maintaining membrane integrity, we have used fluorescence spectroscopy, fluorescence resonance energy transfer, and photocrosslinking to examine various aspects of integration intermediates with different numbers of transmembrane segments (TMSs) from the point of view of the nascent chain. Specifically, we have now characterized how sequential TMSs in the nascent chain regulate the closing and opening of opposite ends of the translocon pore by incorporating a fluorescent or photoreactive probe into the nascent chain using chemically‐modified aminoacyl‐tRNA derivatives, an experimental approach that we originated. (Supported by NIH grant GM 26494 and the Robert A. Welch Foundation.)