title: Differential lipid dependence of the function of bacterial sodium channels.
abstract: The lipid bilayer is important for maintaining the integrity of cellular compartments and plays a vital role in providing the hydrophobic and charged interactions necessary for membrane protein structure, conformational flexibility and function. To directly assess the lipid dependence of activity for voltage-gated sodium channels, we compared the activity of three bacterial sodium channel homologues (NaChBac, NavMs, and NavSp) by cumulative (22)Na(+) uptake into proteoliposomes containing a 3∶1 ratio of 1-palmitoyl 2-oleoyl phosphatidylethanolamine and different "guest" glycerophospholipids. We observed a unique lipid profile for each channel tested. NavMs and NavSp showed strong preference for different negatively-charged lipids (phosphatidylinositol and phosphatidylglycerol, respectively), whilst NaChBac exhibited a more modest variation with lipid type. To investigate the molecular bases of these differences we used synchrotron radiation circular dichroism spectroscopy to compare structures in liposomes of different composition, and molecular modeling and electrostatics calculations to rationalize the functional differences seen. We then examined pore-only constructs (with voltage sensor subdomains removed) and found that in these channels the lipid specificity was drastically reduced, suggesting that the specific lipid influences on voltage-gated sodium channels arise primarily from their abilities to interact with the voltage-sensing subdomains.
authors.affiliation: Department of Physiology and GEPROM (Group d'étude des Proteins Membranaires), Université de Montréal, Montréal, Québec, Canada.
authors.forename: Nazzareno
authors.initials: N
authors.lastname: D'Avanzo
authors.forename: Emily C
authors.initials: EC
authors.lastname: McCusker
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Powl
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Miles
authors.forename: Colin G
authors.initials: CG
authors.lastname: Nichols
authors.forename: B A
authors.initials: BA
authors.lastname: Wallace
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000378:metabolism*; D002942:Circular Dichroism; D015870:Gene Expression; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D050356:Lipid Metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D011487:Protein Conformation; D016415:Sequence Alignment; D012964:Sodium / Q000378:metabolism; D055672:Static Electricity; D061566:Voltage-Gated Sodium Channels / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D008051:Lipid Bilayers; D019269:Phosphatidylinositol 4,5-Diphosphate; D061566:Voltage-Gated Sodium Channels; D012964:Sodium