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Structural determinants of SecB recognition by SecA in bacterial protein translocation

Nature Structural & Molecular Biology volume 10, pages 942–947 (2003)Cite this article

Abstract

SecB is a bacterial chaperone involved in directing pre-protein to the translocation pathway by its specific interaction with the peripheral membrane ATPase SecA. The SecB-binding site on SecA is located at its C terminus and consists of a stretch of highly conserved residues. The crystal structure of SecB in complex with the C-terminal 27 amino acids of SecA from Haemophilus influenzae shows that the SecA peptide is structured as a CCCH zinc-binding motif. One SecB tetramer is bound by two SecA peptides, and the interface involves primarily salt bridges and hydrogen bonding interactions. The structure explains the importance of the zinc-binding motif and conserved residues at the C terminus of SecA in its high-affinity binding with SecB. It also suggests a model of SecB-SecA interaction and its implication for the mechanism of pre-protein transfer in bacterial protein translocation.

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Figure 1: Overall structure of the SecB–SecAc complex.
Figure 2: The structure of SecAc.
Figure 3: Specific interactions between SecB and SecAc.
Figure 4: A model of the SecB–SecA molecular complex.

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Acknowledgements

We thank J. Stuckey for maintaining the X-ray facility at the University of Michigan Medical School, K. Yoshino for making the GST fusion construct, D. Peisach for help in data collection and crystallography, K. Brister for access and help at the Advanced Photon Source BioCARs beamline 14-BM-C, and C. Fierke and R. Matthews for critically reading the manuscript. This work was supported by a US National Institutes of Health grant to Z.X. and the University of Michigan Biological Scholar Program. Z.X. is a Pew scholar in Biomedical Sciences.

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  1. Department of Biological Chemistry and Life Sciences Institute, University of Michigan Medical School, 1301 E. Catherine Road, Ann Arbor, 48109-0606, Michigan

    Jiahai Zhou & Zhaohui Xu

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Correspondence to Zhaohui Xu.

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Zhou, J., Xu, Z. Structural determinants of SecB recognition by SecA in bacterial protein translocation. Nat Struct Mol Biol 10, 942–947 (2003). https://doi.org/10.1038/nsb980

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