Cardiolipin is essential for higher proton translocation activity of reconstituted F-o

The F, membrane domain of F0F1-ATPase complex had been purified from porcin e heart mitochondria. SDS-PAGE with silver staining indicated that the puri ty of F, was about 85% and the sample contained no subunits of F-1-ATPase, The purified F, was reconstituted into liposomes with different phospholipi d composition, and the effect of CL (cardiolipin), PA (phosphatidic acid), PI (phosphatidylinositol) and PS (phosphatidylserine) on the H+ translocati on activity of F, was investigated. The results demonstrated that CL, PA an d Pi could promote the proton translocation of F, with the order of CL > PA much greater than PI, while PS inhibited it. Meanwhile ADM (adriamycin) se verely impaired the proton translocation activity of F, vesicles containing CL, which suggested that CL's stimulation of the activity of reconstituted F, might correlate with its non-bilayer propensity. After F, was incorpora ted into the liposomes containing PE (phosphatidylethanolamine), DOPE (diol eoylphosphatidylethanolamine) as well as DEPE (dielaidoylphosphatidylethano lamine), it was found that the proton translocation activity of F, vesicles increased with the increasing content of PE or DOPE, which has high propen sity of forming non-bilayer structure, but was independent of DEPE. The dyn amic quenching of the intrinsic fluorescence of tryptophan by HE (hypocrell in B) as well as fluorescent spectrum of acrylodan labeling F-0 at cysteine indicated that CL could induce F-0 to a suitable conformation resulting in higher proton translocation activity.