Our studies in 1978-1979 will be concentrated on the four complexes (I, II, III and IV) of the mitochondrial electron transfer chain (each of which corresponds to an energy coupling system) and on transhydrogenase, an energy coupling system closely associated with Complex I. The following lines of endeavor constitute the most crucial aspects in the dissection of the energy coupling systems of the mitochonrial electron transfer chain: a. Isolation and identification of the subunits in ETC and ITC; b. Ion transport function of ITC and how the subunits of ITC implement this function; c. Reconstitution of enzymic activity by recombination of ETC and ITC; d. Subunit requirements for membrane formation; which subunits are intrinsic parts of the unit of membrane formation; e. Sequence of components in the ETC and ITC; g. Evidence for two separate ETC chains in each complex; h. Evidence for the ETC/ITC arrangement in all four complexes of the mitochondrial electron transfer and in transhydrogenase.