Integrating mass spectrometry with MD simulations reveals the role of lipids in Na +/H + antiporters

Nat Commun. 2017 Jan 10;8:13993. doi: 10.1038/ncomms13993.

Abstract

Na+/H+ antiporters are found in all kingdoms of life and exhibit catalysis rates that are among the fastest of all known secondary-active transporters. Here we combine ion mobility mass spectrometry and molecular dynamics simulations to study the conformational stability and lipid-binding properties of the Na+/H+ exchanger NapA from Thermus thermophilus and compare this to the prototypical antiporter NhaA from Escherichia coli and the human homologue NHA2. We find that NapA and NHA2, but not NhaA, form stable dimers and do not selectively retain membrane lipids. By comparing wild-type NapA with engineered variants, we show that the unfolding of the protein in the gas phase involves the disruption of inter-domain contacts. Lipids around the domain interface protect the native fold in the gas phase by mediating contacts between the mobile protein segments. We speculate that elevator-type antiporters such as NapA, and likely NHA2, use a subset of annular lipids as structural support to facilitate large-scale conformational changes within the membrane.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antiporters / chemistry
  • Antiporters / genetics
  • Antiporters / metabolism
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism
  • Escherichia coli Proteins / chemistry
  • Escherichia coli Proteins / metabolism
  • Lipid Metabolism
  • Lipids / chemistry*
  • Mass Spectrometry / methods*
  • Molecular Dynamics Simulation
  • Protein Domains
  • Protein Stability
  • Protein Unfolding
  • Sodium-Hydrogen Exchangers / chemistry*
  • Sodium-Hydrogen Exchangers / genetics
  • Sodium-Hydrogen Exchangers / metabolism*
  • Thermus thermophilus / chemistry

Substances

  • Antiporters
  • Bacterial Proteins
  • Escherichia coli Proteins
  • Lipids
  • NHA2 protein, human
  • NhaA protein, E coli
  • Sodium-Hydrogen Exchangers