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Probing the SecYEG translocation pore size with preproteins conjugated with sizable rigid spherical molecules

Bonardi, F., Halza, E., Walko, M., Du Plessis, F., Nouwen, N., Feringa, B. L. & Driessen, A. J. M., 10-May-2011, In : Proceedings of the National Academy of Sciences of the United States of America. 108, 19, p. 7775-7780 6 p.

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Protein translocation in Escherichia coli is mediated by the translocase that in its minimal form consists of the protein-conducting channel SecYEG, and the motor protein, SecA. SecYEG forms a narrow pore in the membrane that allows passage of unfolded proteins only. Molecular dynamics simulations suggest that the maximal width of the central pore of SecYEG is limited to 16 angstrom. To access the functional size of the SecYEG pore, the precursor of outer membrane protein A was modified with rigid spherical tetraarylmethane derivatives of different diameters at a unique cysteine residue. SecYEG allowed the unrestricted passage of the precursor of outer membrane protein A conjugates carrying tetraarylmethanes with diameters up to 18 angstrom, whereas a 29 angstrom sized molecule blocked the translocation pore. Translocation of the protein-organic molecule hybrids was strictly proton motive force-dependent and occurred at a single pore. With an average diameter of an unfolded polypeptide chain of 4-6 angstrom, the pore accommodates structures of at least 22-24 angstrom, which is vastly larger than the predicted maximal width of a single pore by molecular dynamics simulations.

Original languageEnglish
Pages (from-to)7775-7780
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number19
Publication statusPublished - 10-May-2011

    Keywords

  • secretion, Sec-system, PROTEIN-CONDUCTING CHANNEL, EVERTED MEMBRANE-VESICLES, ESCHERICHIA-COLI, TRANSLATING RIBOSOME, LATERAL GATE, SECA, COMPLEX, DOMAIN, PRLA, STABILIZES

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