Synthesis and Discharge of the Coupling Factor·Adenosine Diphosphate Complex in Spinach Chloroplast Lamellae

The formation of a coupling factor.ADP complex is shown to be dependent on photoinduced electron transport, AMP, and P(i), and sensitive to arsenate and sulfate. The stability of the complex is unaffected by subsequent addition of arsenate, but is quite markedly sensitive to the addition of ADP. The data are discussed in relation to possible models of photophosphorylation, and in particular, to one in which coupling factor-bound, photosynthetically generated, ADP serves as a phosphoryl donor to substrate ADP.