Three proton pumps, morphology and movements

The diameter of F1 coupling factor and the distance it protrudes from the membrane of bovine heart submitochondrial particles were measured quantitatively using horse spleen ferritin as a standard. Employing the freeze-etch technique, particles of similar size were found on membranes of submitochondrial particles and on membranes of particles first depleted by F1, then reconstituted by addition of F1. The extramembranous size of F1 is 9.7 nm and F1 protrudes from the membrane surface by about 13.6 nm. Bacteriorhodopsin and cytochrome oxidase were incorporated into lipids derived from membranes of extremely thermoacidophilic microorganisms by the octylglucoside dilution method. The bacteriorhodopsin pump was fully functional provided high concentrations of valinomycin were added. With decanoyl-N-methylglucamide as detergent the pump was very active in the absence of valinomycin. Concentrations of gramicidin that collapsed the delta pH in bacteriorhodopsin liposomes prepared with soybean phospholipid had little or no effect on these rigid proteoliposomes. Very high concentrations (30 micrograms per ml) were partially effective, suggesting a mechanism other than formation of a gramicidin dimer channel. Cytochrome oxidase lost virtually all activity when incorporated into these rigid liposomes but was fully reactivated on addition of suitable detergents.