Specific cardiolipin–SecY interactions are required for proton-motive force stimulation of protein secretion

Robin A. Corey, Euan Pyle, William J. Allen, Daniel W. Watkins, Marina Casiraghi, Bruno Miroux, Ignacio Arechaga, Argyris Politis, Ian Collinson*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

26 Citations (Scopus)
278 Downloads (Pure)

Abstract

The transport of proteins across or into membranes is a vital biological process, achieved in every cell by the conserved Sec machinery. In bacteria, SecYEG combines with the SecA motor protein for secretion of preproteins across the plasma membrane, powered by ATP hydrolysis and the transmembrane proton-motive force (PMF). The activities of SecYEG and SecA are modulated by membrane lipids, particularly cardiolipin (CL), a specialized phospholipid known to associate with a range of energy-transducing machines. Here, we identify two specific CL binding sites on the Thermotoga maritima SecA–SecYEG complex, through application of coarse-grained molecular dynamics simulations. We validate the computational data and demonstrate the conserved nature of the binding sites using in vitro mutagenesis, native mass spectrometry, biochemical analysis, and fluorescence spectroscopy of Escherichia coli SecYEG. The results show that the two sites account for the preponderance of functional CL binding to SecYEG, and mediate its roles in ATPase and protein transport activity. In addition, we demonstrate an important role for CL in the conferral of PMF stimulation of protein transport. The apparent transient nature of the CL interaction might facilitate proton exchange with the Sec machinery, and thereby stimulate protein transport, by a hitherto unexplored mechanism. This study demonstrates the power of coupling the high predictive ability of coarse-grained simulation with experimental analyses, toward investigation of both the nature and functional implications of protein–lipid interactions.

Original languageEnglish
Pages (from-to)7967-7972
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number31
Early online date16 Jul 2018
DOIs
Publication statusPublished - 31 Jul 2018

Keywords

  • Cardiolipin
  • Molecular dynamics
  • Native mass spectrometry
  • Protein translocation
  • SecYEG

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