Studies are being conducted on an apparent mutant from Azotobacter vinelandii. One mutation involves the deletion of cytochrome c4 and c5 from the respiratory chain. As a consequence oxidative phosphorylation as well as enzymes from the glycolytic and Krebs cycles have greatly declined in specific activity. Nevertheless cell yield and growth have diminished only slightly. A mechanism is being examined which provides ATP for cell growth from substrate-linked phosphorylation rather than oxidative phosphorylation. ATPase from wild-type A. vinelandii has been successfully solubilized by a new procedure. After purification to homogeneity by chromatographic methods, the interaction of trypsin with a control subunit inhibitor will be examined. Cytochrome c3 from Desulfovibrio vulgaris--a unique four-electron acceptor of negative redox potential is being studied as a model system for cytochrome c oxidase and for heme-heme interaction. The interaction of phospholipids with c3 will be examined by optical and EPR spectroscopy in order to ascertain a possible role for these compounds on the hemoprotein's redox properties.