Energy landscape steering mediates dynamic coupling in ATP-driven protein translocation by the bacterial Sec machinery
Year: 2019
Type: preprint
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.
DOI: 10.1101/793943
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: green
Awards: G119964413, G12500569, G176604203, G2270948041, G265847165, G291036901, G3111088154, G3230480383, G3310574491, G3490171961, G3810972741, G4131035492, G4280972364, Deciphering the allosteric mechanism of protein translocation through membranes, G496129201, G5202290780, Ensemble and single molecule analysis of protein translocation, G5912748629, G5916014575, Allosteric communication in membrane protein complexes linked to conformational transitions on multiple timescales, G7003443856, Deciphering the allosteric mechanism of protein translocation through membranes, G7379506900, Understanding mitochondrial protein import and membrane insertion.
OpenAlex ID: W2978205448