The effects of oleic acid on the activity of the reconstituted Ca2+,Mg2+-ATPase

Abstract

labelling ratio, as expected since energy transfer between FITC groups will increase in efficiency with increasing labelling ratio and energy transfer is a depolarizing event. As shown in Table 1, fluorescence polarization is, however, relatively independent of molar ratio of lipid to ATPase, again arguing against the formation of monomeric ATPase species at high dilutions in lipid. Fluorescence polarization is greater for the ATPase reconstituted into gel phase lipid than in liquid crystalline phase lipid (Table 1 ), presumably reflecting restricted motion for the ATPase in gel phase lipid. The experiments reported here suggest that the ATPase is present in reconstituted systems in oligomeric form, relatively independent of lipid-to-protein ratios. These oligomers are envisaged as dynamic crystalline arrays, continually forming and breaking up within the membrane (Napier et a[., 1987).