HDX-MS reveals nucleotide-dependent, anti-correlated opening and closure of SecA and SecY channels of the bacterial translocon

eLife

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[1] Department of Biochemistry, University of Oxford, Oxford, United Kingdom;Department of Chemistry, King's College London, London, United Kingdom;Department of Chemistry, King's College London, London, United Kingdom;Department of Chemistry, Imperial College London, London, United Kingdom;School of Biochemistry, University of Bristol, Bristol, United Kingdom;

关键词: hydrogen-deuterium exchange mass spectromtery;    conformational dynamics;    SecA;    SecYEG;    protein translocation;    E. coli;   

DOI  :  10.7554/eLife.47402

来源: publisher

【 摘 要 】

10.7554/eLife.47402.001The bacterial Sec translocon is a multi-protein complex responsible for translocating diverse proteins across the plasma membrane. For post-translational protein translocation, the Sec-channel – SecYEG – associates with the motor protein SecA to mediate the ATP-dependent transport of pre-proteins across the membrane. Previously, a diffusional-based Brownian ratchet mechanism for protein secretion has been proposed; the structural dynamics required to facilitate this mechanism remain unknown. Here, we employ hydrogen-deuterium exchange mass spectrometry (HDX-MS) to reveal striking nucleotide-dependent conformational changes in the Sec protein-channel from Escherichia coli. In addition to the ATP-dependent opening of SecY, reported previously, we observe a counteracting, and ATP-dependent, constriction of SecA around the pre-protein. ATP binding causes SecY to open and SecA to close; while, ADP produced by hydrolysis, has the opposite effect. This alternating behaviour could help impose the directionality of the Brownian ratchet for protein transport through the Sec machinery.

【 授权许可】

CC BY