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Structural analysis of substrate binding by the TatBC component of the twin-arginine protein transport system

Tarry, M.J. and Schafer, Eva and Chen, S.Y. and Buchanan, G. and Greene, N.P. and Lea, S.M. and Palmer, T. and Saibil, Helen R. and Berks, B.C. (2009) Structural analysis of substrate binding by the TatBC component of the twin-arginine protein transport system. Proceedings of the National Academy of Sciences of the United States of America 106 (32), pp. 13284-13289. ISSN 0027-8424.

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Official URL: http://dx.doi.org/10.1073/pnas.0901566106

Abstract

The Tat system transports folded proteins across the bacterial cytoplasmic membrane and the thylakoid membrane of plant chloroplasts. In Escherichia coli substrate proteins initially bind to the integral membrane TatBC complex which then recruits the protein TatA to effect translocation. Overproduction of TatBC and the substrate protein SufI in the absence of TatA led to the accumulation of TatBC-SufI complexes that could be purified using an affinity tag on the substrate. Three-dimensional structures of the TatBC-SufI complexes and unliganded TatBC were obtained by single-particle electron microscopy and random conical tilt reconstruction. Comparison of the structures shows that substrate molecules bind on the periphery of the TatBC complex and that substrate binding causes a significant reduction in diameter of the TatBC part of the complex. Although the TatBC complex contains multiple copies of the signal peptide-binding TatC protomer, purified TatBC-SufI complexes contain only 1 or 2 SufI molecules. Where 2 substrates are present in the TatBC-SufI complex, they are bound at adjacent sites. These observations imply that only certain TatC protomers within the complex interact with substrate or that there is a negative cooperativity of substrate binding. Similar TatBC-substrate complexes can be generated by an alternative in vitro reconstitution method and using a different substrate protein.

Item Type: Article
School or Research Centre: Birkbeck Schools and Research Centres > School of Science > Biological Sciences
Depositing User: Administrator
Date Deposited: 04 Aug 2010 14:09
Last Modified: 17 Apr 2013 12:17
URI: http://eprints.bbk.ac.uk/id/eprint/1080

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