title: Integrating mass spectrometry with MD simulations reveals the role of lipids in Na+/H+antiporters.
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.
authors.affiliation: Department of Chemistry, Physical &Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Landreh
authors.affiliation: Department of Chemistry, Physical &Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK.|Department of Chemistry-BMC, Uppsala University, Box 576, Uppsala SE-751 23, Sweden.
authors.forename: Erik G
authors.initials: EG
authors.lastname: Marklund
authors.affiliation: Centre for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden.
authors.forename: Povilas
authors.initials: P
authors.lastname: Uzdavinys
authors.affiliation: Department of Chemistry, Physical &Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK.
authors.forename: Matteo T
authors.identifier: 0000-0003-4672-471X
authors.initials: MT
authors.lastname: Degiacomi
authors.affiliation: Centre for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden.
authors.forename: Mathieu
authors.identifier: 0000-0002-3928-7155
authors.initials: M
authors.lastname: Coincon
authors.affiliation: Department of Chemistry, Physical &Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK.
authors.forename: Joseph
authors.identifier: 0000-0001-7686-2983
authors.initials: J
authors.lastname: Gault
authors.affiliation: Department of Chemistry, Physical &Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK.
authors.forename: Kallol
authors.initials: K
authors.lastname: Gupta
authors.affiliation: Department of Chemistry, Physical &Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK.
authors.forename: Idlir
authors.initials: I
authors.lastname: Liko
authors.affiliation: Department of Chemistry, Physical &Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK.
authors.forename: Justin L P
authors.initials: JL
authors.lastname: Benesch
authors.affiliation: Centre for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden.
authors.forename: David
authors.initials: D
authors.lastname: Drew
authors.affiliation: Department of Chemistry, Physical &Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK.
authors.forename: Carol V
authors.initials: CV
authors.lastname: Robinson
mesh_terms: D017920:Antiporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*; D056004:Molecular Dynamics Simulation; D000072417:Protein Domains; D055550:Protein Stability; D058767:Protein Unfolding; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016963:Thermus thermophilus / Q000737:chemistry
chemical_list: D017920:Antiporters; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008055:Lipids; C102839:NhaA protein, E coli; C527589:SLC9B2 protein, human; D017923:Sodium-Hydrogen Exchangers