title: Influence of lipids on membrane assembly and stability of the potassium channel KcsA.
abstract: Recently we observed in an in vitro system that newly synthesized KcsA assembles efficiently into a tetramer in lipid vesicles [van Dalen et al. (2002) FEBS Lett. 511, 51-58]. Here we used this system to get insight into the importance of the lipid composition for KcsA membrane association and tetramerization and we compared this to the lipid dependency of the thermo-stability of the KcsA tetramer. It was found that a large amount of phosphatidylethanolamine (>40 mol%) and a lower amount of phosphatidylglycerol (approximately 20-30 mol%) were optimal for efficient KcsA membrane association and tetramerization. Strikingly, vesicles of the abundant and commonly used membrane lipid phosphatidylcholine did not support assembly, further demonstrating the importance of membrane lipid composition for KcsA assembly. The in vitro assembled KcsA tetramer showed similar thermo-stability in biological and pure lipid membranes, demonstrating that both tetramers are alike. In addition, we show that solubilization of the membrane with detergent reduces the thermo-stability of the tetramer. The highest KcsA tetramer stability was observed in intact bilayers in the presence of anionic lipids.
authors.affiliation: Department Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands. a.vandalen@chem.uu.nl
authors.forename: Annemieke
authors.initials: A
authors.lastname: van Dalen
authors.forename: Sander
authors.initials: S
authors.lastname: Hegger
authors.forename: J Antoinette
authors.initials: JA
authors.lastname: Killian
authors.forename: Ben
authors.initials: B
authors.lastname: de Kruijff
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D002474:Cell-Free System; D003902:Detergents / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D008051:Lipid Bilayers / Q000737:chemistry; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000737:chemistry; D015221:Potassium Channels / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D011489:Protein Denaturation; D012995:Solubility; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D003902:Detergents; D008051:Lipid Bilayers; D008055:Lipids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010715:Phosphatidylglycerols; D015221:Potassium Channels; C107790:prokaryotic potassium channel