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Type: Journal article
Title: The TatA component of the twin-arginine protein transport system forms channel complexes of variable diameter
Author: Gohlke, U.
Pullan, L.
McDevitt, C.
Porcelli, I.
de Leeuw, E.
Palmer, T.
Saibil, H.
Berks, B.
Citation: Proceedings of the National Academy of Sciences of the United States of America, 2005; 102(30):10482-10486
Publisher: Natl Acad Sciences
Issue Date: 2005
ISSN: 0027-8424
Statement of
Ulrich Gohlke, Lee Pullan, Christopher A. McDevitt, Ida Porcelli, Erik de Leeuw, Tracy Palmer, Helen R. Saibil, and Ben C. Berks
Abstract: The Tat system mediates Sec-independent transport of folded precursor proteins across the bacterial plasma membrane or the chloroplast thylakoid membrane. Tat transport involves distinct high-molecular-weight TatA and TatBC complexes. Here we report the 3D architecture of the TatA complex from Escherichia coli obtained by single-particle electron microscopy and random conical tilt reconstruction. TatA forms ring-shaped structures of variable diameter in which the internal channels are large enough to accommodate known Tat substrate proteins. This morphology strongly supports the proposal that TatA forms the protein-conducting channel of the Tat system. One end of the channel is closed by a lid that might gate access to the channel. On the basis of previous protease accessibility measurements, the lid is likely to be located at the cytoplasmic side of the membrane. The observed variation in TatA diameter suggests a model for Tat transport in which the number of TatA protomers changes to match the size of the channel to the size of the substrate being transported. Such dynamic close packing would provide a mechanism to maintain the membrane permeability barrier during transport.
Keywords: conical tilt reconstruction; electron microscopy, Tat protein transport; three-dimensional structure; twin-arginine signal peptide.
Description: © 2005 by The National Academy of Sciences of the USA
RMID: 0020093547
DOI: 10.1073/pnas.0503558102
Appears in Collections:Molecular and Biomedical Science publications

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