Comparison of the effects of one‐side‐ and two‐side Mg2+ on the reconstitution of mitochondrial H+‐ATPase

Abstract

Three types of proteoliposome containing mitochondrial H+-ATPase have been prepared: Mg2+-‘free’, one-side and two-side Mg2+-containing proteoliposomes. The ATPase activity as well as its sensitivity to oligomycin or N,N'-dicyclohexylcarbodiimide of the three proteoliposome preparations has been compared. They decreased in the order : L ·(H+-ATPase)+Mg2+ > L · (H+-ATPase)+Mg2+ > L · (H+-ATPase)−Mg2+. The fluidity of the proteoliposomes has also been compared by fluorescence polarization probes diphenylhexatriene (DPH) or 7-(9-anthroyloxy)stearic acid (7-AS). The degree of polarization for DPH in these proteoliposomes decreased in the order: L · (H+-ATPase)+Mg2+ > L · (H+-ATPase)+Mg2+ > L · (H+-ATPase)−Mg2+, while that for 7-AS: L · (H+-ATPase)+Mg2+ ≈ L · (H+-ATPase)+Mg2+ > L · (H+-ATPase)−Mg2+.Lipid fluidityMitochondrial H+-ATPaseOne-side Mg2+ effectTwo-side Mg2+ effectLipid-protein interactio