The ATP synthase of mitochondria, chloroplasts and bacteria taps the energy of a transmembrane proton gradient to synthesize ATP. The mechanism of this important energy- conserving process is not understood in molecular terms. The enzyme is comprised of two portions, F0, which is an integral, membrane-spanning proton channel, and F1 which is peripheral to the membrane and contains the catalytic sites. Together F0 and F1 contain more than eight different protein subunits with a minimum of seventeen polypeptide chains. Three of the F1 subunits have been isolated in reconstitutively active forms from the chloroplast enzyme (CF1), and attempts to isolate the remaining two for use in reconstitution studies aimed at elucidating subunit structure-function relationships will be under taken. Other studies will aim at obtaining structural information for the B subunit which contains part or all of the catalytic site. Chemical modification with fluorescent and photoaffinity probes will be employed to map specific sites on the B subunit within the CF1 complex and to identify amino acid residues involved in, for example, nucleotide binding. Monoclonal antibodies will be used to identify sites of contact between the B subunit and other subunits of the ATP synthase. When plants capture sunlight they convert the radiant energy into chemical energy which supports the synthesis of plant constituents. The latter provide, directly or indirectly, the nutrients of animals, including man. The energy conversion process is complex and is catalyzed by a set of proteins in the chloroplast membrane. Several of these have been isolated and the PI wishes to isolate and characterize others so that eventually the whole complex can be reconstituted in a functional form.
