Interactions between ADP and the coupling factor of photophosphorylation.
The coupling factor of photophosphorylation, which carries out the terminal steps in the light-dependent synthesis of ATP in spinach chloroplasts, forms tight complexes with [(14)C]ADP in vitro. The bound [(14)C]ADP undergoes a transphosphorylation reaction to give [(14)C]AMP and [(14)C]ATP. The [(14)C]ATP remains tightly bound, and can be recovered conveniently only by denaturation of the enzyme nucleotide complex. If spinach membranes are illuminated in the presence of pyocyanine and [(3)H]AMP or [(32)P]P(i), the enzyme can be recovered as a tight complex with [(3)H]ADP or [(32)P]ADP. The evidence indicates that AMP is an earlier acceptor of phosphate than is ADP, in a light-driven phosphorylation reaction. It also suggests that AMP serves as a cofactor in photophosphorylation.
D000227:Adenine Nucleotides / Q000096:biosynthesis / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000096:biosynthesis; D001665:Binding Sites; D002247:Carbon Isotopes; D002499:Centrifugation, Density Gradient; D002736:Chloroplasts
D000227:Adenine Nucleotides; D002247:Carbon Isotopes; D000255:Adenosine Triphosphate