3mp7

Publication Abstract from PubMed

The structure of the protein-translocating channel SecYEbeta from Pyrococcus furiosus at 3.1-A resolution suggests a mechanism for chaperoning transmembrane regions of a protein substrate during its lateral delivery into the lipid bilayer. Cytoplasmic segments of SecY orient the C-terminal alpha-helical region of another molecule, suggesting a general binding mode and a promiscuous guiding surface capable of accommodating diverse nascent chains at the exit of the ribosomal tunnel. To accommodate this putative nascent chain mimic, the cytoplasmic vestibule widens, and a lateral exit portal is opened throughout its entire length for partition of transmembrane helical segments to the lipid bilayer. In this primed channel, the central plug still occludes the pore while the lateral gate is opened, enabling topological arbitration during early protein insertion. In vivo, a 15 amino acid truncation of the cytoplasmic C-terminal helix of SecY fails to rescue a secY-deficient strain, supporting the essential role of this helix as suggested from the structure.

Lateral opening of a translocon upon entry of protein suggests the mechanism of insertion into membranes.,Egea PF, Stroud RM Proc Natl Acad Sci U S A. 2010 Sep 20. PMID:20855604^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.