The TatA component of the twin-arginine protein transport system forms channel complexes of variable diameter

Ulrich Gohlke, Lee Pullan, Christopher A. McDevitt, Ida Porcelli, Erik de Leeuw, Tracy Palmer, Helen R. Saibil, Ben C. Berks

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    205 Citations (Scopus)


    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.

    Original languageEnglish
    Pages (from-to)10482-10486
    Number of pages5
    JournalProceedings of the National Academy of Sciences of the United States of America
    Issue number30
    Publication statusPublished - 2005

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