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

Zainab Ahdash, Euan Pyle, William John Allen, Robin A Corey, Ian Collinson, Argyris Politis

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)
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Abstract

The 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.

Original languageEnglish
Article numbere47402
JournaleLife
Volume8
Early online date10 Jul 2019
DOIs
Publication statusPublished - 10 Jul 2019

Keywords

  • E. coli
  • SecA
  • SecYEG
  • conformational dynamics
  • hydrogen-deuterium exchange mass spectromtery
  • molecular biophysics
  • protein translocation
  • structural biology

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