Incorporation of the V-ATPase inhibitors concanamycin and indole pentadiene in lipid membranes. Spin-label EPR studies.
The incorporation of concanamycin A, a potent inhibitor of vacuolar ATPases, into membranes of dimyristoyl phosphatidylcholine has been studied by using EPR of spin-labelled lipid chains. At an inhibitor/lipid ratio of 1:1 mol/mol, concanamycin A broadens the chain-melting transition of the phospholipid bilayer membrane, and effects the lipid chain motion in the fluid phase. The outer hyperfine splitting of a spin label at the C-5 position and the line widths of a spin label at the C-14 position of the lipid chain are increased by concanamycin A. Considerably larger membrane perturbations are caused by equimolar admixture of a designed synthetic 5-(5,6-dichloro-2-indolyl)-2,4-pentadienoyl V-ATPase inhibitor. These results indicate that concanamycin A intercalates readily between the lipid chains in biological membranes, with minimal perturbation of the bilayer structure. Essentially identical results are obtained with concanamycin A added to preformed membranes as a concentrated solution in DMSO, or mixed with lipid in organic solvent prior to membrane formation. Therefore, the common mode of addition in V-ATPase inhibition assays ensures incorporation of concanamycin into the lipid bilayer milieu, which provides an efficient channel of access to the transmembrane domains of the V-ATPase.
Páli
Tibor
T
Department of Chemistry, University of Leeds, Leeds LS2 9JT, UK.
Dixon
Neil
N
Kee
Terence P
TP
Marsh
Derek
D
D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D007211:Indoles / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism*; D018942:Macrolides / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D013113:Spin Labels; D013329:Structure-Activity Relationship; D013696:Temperature; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors*
D004791:Enzyme Inhibitors; D007211:Indoles; D008051:Lipid Bilayers; D018942:Macrolides; D013113:Spin Labels; C036978:concanamycin A; D025262:Vacuolar Proton-Translocating ATPases; D004134:Dimyristoylphosphatidylcholine