Reconstitution of Oxidative Phosphorylation and of Oligomycin-Sensitive ATPase by Five- and Six-Subunit Forms of Pea Mitochondrial F(1)-ATPase.
Five- and six-subunit forms of F(1)-ATPase were purified from pea (Pisum sativum L. cv Homesteader) cotyledon submitochondrial particles. Apart from the usual complement of five subunits, the six-subunit enzyme contained an additional 26,500-dalton protein. Both forms of the F(1)-ATPase were used to reconstitute oxidative phosphorylation in F(1)-depleted (ASU) as well as in F(1) and oligomycin-sensitivity conferring protein (OSCP)-depleted (ASUA) bovine mitochondrial membranes. The six-subunit enzyme was considerably more efficient in reconstituting the ATP synthesis than the five-subunit enzyme. Both forms of the enzyme were also able to reconstitute the ATPase activity in ASU- as well as in ASUA-particles. There were substantial differences, however, in the oligomycin sensitivity of the ATPase bound to the ASUA-particles: 20 and 60% inhibition by oligomycin was obtained in the case of the five-subunit and six-subunit enzyme, respectively. We conclude, that the 26,500-dalton protein present in the six-subunit F(1)-ATPase is responsible for the increase in oligomycin sensitivity of the bound enzyme and functions, therefore, as the plant OSCP.
Horak
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Department of Plant Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5.
Packer
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Horak
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