Interaction of Membrane-Bound and Soluble CF 1 with the Photoreactive Nucleotide 3′-0-(4-Benzoyl) Benzoyl ADP

Chloroplast ATP synthetase contains several binding sites: catalytic sites where rapid association and dissociation of nucleotides occur, and tight nucleotide binding sites which may be regulatory (for review see Shavit, 1980; Bar-Zvi, Shavit, 1982). While the number of sites has to be established, they are probably located on the two large subunits (α and β) of CF1. Photoreactive nucleotide analogs are useful for study of the location, function and number of these binding sites. Photoaffinity labeling of soluble CF1 with ADP or ATP analogs resulted in their covalent incorporation into either the β subunit or both the α and β subunits of the enzyme (Carlier et al., 1979; Wapenvoord et al., 1981) Photoaffinity labeling of the tight nucleotide binding site of membrane-bound CF1 with 2-azido ADP (Czarnecki et al., 1982) resulted in its incorporation into the β subunit.