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Nature. 2007 Dec 13;450(7172):1026-30.

Molecular code for transmembrane-helix recognition by the Sec61 translocon.

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Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.


Transmembrane alpha-helices in integral membrane proteins are recognized co-translationally and inserted into the membrane of the endoplasmic reticulum by the Sec61 translocon. A full quantitative description of this phenomenon, linking amino acid sequence to membrane insertion efficiency, is still lacking. Here, using in vitro translation of a model protein in the presence of dog pancreas rough microsomes to analyse a large number of systematically designed hydrophobic segments, we present a quantitative analysis of the position-dependent contribution of all 20 amino acids to membrane insertion efficiency, as well as of the effects of transmembrane segment length and flanking amino acids. The emerging picture of translocon-mediated transmembrane helix assembly is simple, with the critical sequence characteristics mirroring the physical properties of the lipid bilayer.

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