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Transport of proteins across membranes is a fundamental process, achieved in every cell by the 'Sec' translocon. In prokaryotes, SecYEG associates with the motor ATPase SecA to carry out translocation for pre-protein secretion. Previously, we proposed a Brownian ratchet model for transport, whereby the free energy of ATP-turnover favours the directional diffusion of the polypeptide (Allen et al., 2016). Here, we show that ATP enhances this process by modulating secondary structure formation within the translocating protein. A combination of molecular simulation with hydrogendeuterium-exchange mass spectrometry and electron paramagnetic resonance spectroscopy reveal an asymmetry across the membrane: ATP-induced conformational changes in the cytosolic cavity promote unfolded pre-protein structure, while the exterior cavity favours its formation. This ability to exploit structure within a pre-protein is an unexplored area of protein transport, which may apply to other protein transporters, such as those of the endoplasmic reticulum and mitochondria. © 2019, Corey et al.


Robin A Corey, Zainab Ahdash, Anokhi Shah, Euan Pyle, William J Allen, Tomas Fessl, Janet E Lovett, Argyris Politis, Ian Collinson. ATP-induced asymmetric pre-protein folding as a driver of protein translocation through the Sec machinery. eLife. 2019 Jan 02;8

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PMID: 30601115

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