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bioRxiv · 10.1101/793943

Energy landscape steering in SecYEG mediates dynamic coupling in ATP driven protein translocation

Crossley, J.·Watson, M. A.·Fessl, T.·Watkins, D.·Corey, R. A.·Sabir, T.·Radford, S. E.·Collinson, I.·Tuma, R.
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Abstract

The Sec translocon is a highly conserved membrane complex for transport of polypeptides across, or into, lipid bilayers. In bacteria, the core protein-channel SecYEG resides in the inner-membrane, through which secretion is powered by the cytosolic ATPase SecA. Here, we use single-molecule fluorescence to interrogate the dynamic state of SecYEG throughout the hydrolytic cycle of SecA. We show that the SecYEG channel fluctuates between open and closed states faster ([~]20-fold during transport) than ATP turnover; while the nucleotide status of SecA modulates the rates of opening and closure. Interestingly, a SecY variant (PrlA4), exhibiting faster protein transport, but unaffected ATPase rates, increases the dwell time in the open state, facilitating pre-protein diffusion through the pore; thereby improving the efficiency of translocation. Thus, contrary to prevailing structure-based models, SecYEG plays an integral part in the translocation mechanism through dynamic allosteric coupling in which SecA steers the energy landscape of the protein-channel.

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Crossley, J., Watson, M. A., Fessl, T., Watkins, D., Corey, R. A., Sabir, T., Radford, S. E., Collinson, I., Tuma, R.. 2019-10-05. Energy landscape steering in SecYEG mediates dynamic coupling in ATP driven protein translocation. https://doi.org/10.1101/793943

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