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.
- MeSH
- Adenosine Triphosphate chemistry metabolism MeSH
- Adenosine Triphosphatases chemistry metabolism MeSH
- Escherichia coli metabolism MeSH
- Membrane Transport Proteins chemistry metabolism MeSH
- Models, Molecular MeSH
- Protein Precursors metabolism MeSH
- SecA Proteins chemistry metabolism MeSH
- Escherichia coli Proteins chemistry metabolism MeSH
- Protein Folding * MeSH
- SEC Translocation Channels chemistry metabolism MeSH
- Protein Transport MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
