A nexus of intrinsic dynamics underlies translocase priming

Structure. 2021 Aug 5;29(8):846-858.e7. doi: 10.1016/j.str.2021.03.015. Epub 2021 Apr 13.

Abstract

The cytoplasmic ATPase SecA and the membrane-embedded SecYEG channel assemble to form the Sec translocase. How this interaction primes and catalytically activates the translocase remains unclear. We show that priming exploits a nexus of intrinsic dynamics in SecA. Using atomistic simulations, smFRET, and HDX-MS, we reveal multiple dynamic islands that cross-talk with domain and quaternary motions. These dynamic elements are functionally important and conserved. Central to the nexus is a slender stem through which rotation of the preprotein clamp of SecA is biased by ATPase domain motions between open and closed clamping states. An H-bonded framework covering most of SecA enables multi-tier dynamics and conformational alterations with minimal energy input. As a result, cognate ligands select preexisting conformations and alter local dynamics to regulate catalytic activity and clamp motions. These events prime the translocase for high-affinity reception of non-folded preprotein clients. Dynamics nexuses are likely universal and essential in multi-liganded proteins.

Keywords: HDX-MS; MD simulation; SecA; SecYEG channel; graph analysis; intrinsic dynamics; protein secretion; signal peptide; smFRET; translocase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus subtilis / enzymology*
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism
  • Catalytic Domain
  • Hydrogen Bonding
  • Models, Molecular
  • Molecular Dynamics Simulation
  • Multiprotein Complexes / chemistry
  • Protein Binding
  • Protein Conformation
  • Protein Domains
  • SEC Translocation Channels / metabolism*
  • SecA Proteins / chemistry*
  • SecA Proteins / metabolism*

Substances

  • Bacterial Proteins
  • Multiprotein Complexes
  • SEC Translocation Channels
  • SecA Proteins