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Asymmetric binding between SecA and SecB two symmetric proteins: implications for function in export

Randall, L.L., Crane, J.M., Lilly, A.A., Liu, G., Mao, C., Patel, C.N. and Hardy, S.J.S. (2005) Asymmetric binding between SecA and SecB two symmetric proteins: implications for function in export. Journal of Molecular Biology, 348 (2). pp. 479-489. ISSN 0022-2836

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SecB, a small tetrameric chaperone in Escherichia coli, facilitates export of precursor polypeptides from the cytoplasm to the periplasmic space. During this process, SecB displays two modes of binding. As a chaperone, it binds promiscuously to precursors to maintain them in a non-native conformation. SecB also demonstrates specific recognition of, and binding to, SecA. SecB with the precursor tightly bound enters an export-active complex with SecA and must pass the ligand to SecA at the translocon in the membrane. Here we use variants of SecA and SecB to further probe these interactions. We show that, unexpectedly, the binding between the two symmetric molecules is asymmetric and that the C-terminal α-helices of SecB bind in the interfacial region of the SecA dimer. We suggest that disruption of this interface by SecB facilitates conformational changes of SecA that are crucial to the transfer of the precursor from SecB to SecA.

Item Type: Article
Institution: The University of York
Academic Units: The University of York > Biology (York)
Depositing User: York RAE Import
Date Deposited: 21 Apr 2009 11:20
Last Modified: 21 Apr 2009 11:20
Published Version: http://dx.doi.org/10.1016/j.jmb.2005.02.036
Status: Published
Publisher: Elsevier Science B.V., Amsterdam
Identification Number: 10.1016/j.jmb.2005.02.036
URI: http://eprints.whiterose.ac.uk/id/eprint/6784

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