Glycocardiolipin modulates the surface interaction of the proton pumped by bacteriorhodopsin in purple membrane preparations.
Glycocardiolipin is an archaeal analogue of mitochondrial cardiolipin, having an extraordinary affinity for bacteriorhodopsin, the photoactivated proton pump in the purple membrane of Halobacterium salinarum. Here purple membranes have been isolated by osmotic shock from either cells or envelopes of Hbt. salinarum. We show that purple membranes isolated from envelopes have a lower content of glycocardiolipin than standard purple membranes isolated from cells. The properties of bacteriorhodopsin in the two different purple membrane preparations are compared; although some differences in the absorption spectrum and the kinetic of the dark adaptation process are present, the reduction of native membrane glycocardiolipin content does not significantly affect the photocycle (M-intermediate rise and decay) as well as proton pumping of bacteriorhodopsin. However, interaction of the pumped proton with the membrane surface and its equilibration with the aqueous bulk phase are altered.
Dipartimento di Biochimica medica, biologia medica e fisica medica. Università degli Studi di Bari, Piazza G. Cesare, I-70124 Bari, Italy.
Angela
A
Corcelli
Simona
S
Lobasso
Matilde Sublimi
MS
Saponetti
Andreas
A
Leopold
Norbert A
NA
Dencher
D001436:Bacteriorhodopsins / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D002308:Cardiolipins / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D019617:Halobacterium salinarum / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D017494:Proton Pumps / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D011522:Protons; D018717:Purple Membrane / Q000187:drug effects* / Q000502:physiology*; D013499:Surface Properties
D002308:Cardiolipins; D017494:Proton Pumps; D011522:Protons; D001436:Bacteriorhodopsins