Lipids in the structure, folding, and function of the KcsA K+ channel.
Lipid molecules surround an ion channel in its native environment of cellular membranes. The importance of the lipid bilayer and the role of lipid protein interactions in ion channel structure and function are not well understood. Here we demonstrate that the bacterial potassium channel KcsA binds a negatively charged lipid molecule. We have defined the potential binding site of the lipid molecule on KcsA by X-ray crystallographic analysis of a complex of KcsA with a monoclonal antibody Fab fragment. We also demonstrate that lipids are required for the in vitro refolding of the KcsA tetramer from the unfolded monomeric state. The correct refolding of the KcsA tetramer requires lipids, but it is not dependent on negatively charged lipids as refolding takes place in the absence of such lipids. We confirm that the presence of negatively charged lipids is required for ion conduction through the KcsA potassium channel, suggesting that the lipid bound to KcsA is important for ion channel function.
Valiyaveetil
Francis I
FI
Howard Hughes Medical Institute, Laboratory of Molecular Neurobiology and Biophysics, Rockefeller University, 1230 York Avenue, New York, New York 10021, USA.
Zhou
Yufeng
Y
MacKinnon
Roderick
R
D000911:Antibodies, Monoclonal / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D001666:Binding Sites, Antibody; D003460:Crystallization; D018360:Crystallography, X-Ray; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D010710:Phosphates / Q000032:analysis; D010743:Phospholipids / Q000032:analysis; D015221:Potassium Channels / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D012414:Rubidium Radioisotopes / Q000378:metabolism; D013329:Structure-Activity Relationship
D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D008051:Lipid Bilayers; D010710:Phosphates; D010743:Phospholipids; D015221:Potassium Channels; D012414:Rubidium Radioisotopes; C107790:prokaryotic potassium channel