[The action of dinactin on cyclic photophosphorylation, on the light-triggered ATP-Pi exchange reaction and on the light-induced proton transport in chloroplasts].

Dinactin, an antibiotic forming complexes with K(+) ions, uncouples phosphorylation in chloroplasts without requiring the presence of a substance increasing the permeability of the membrane for protons. To inhibit photophosphorylation, less Dinactin is necessary in the absence than in the presence of K(+).When added before the light phase, Dinactin affects the light-triggered ATP-Pi exchange reaction in the same way as it does the complete photophosphorylation. Addition of the antibiotic after the activation by light inhibits the exchange reaction independently of the presence of K(+), possibly by blocking the energy transfer to ATP.The inhibition of the light-induced proton transport by Dinactin is more pronounced in the presence of K(+) than of Na(+) ions. The manner in which changes in the permeability of the chloroplast membrane for K(+) ions caused by Dinactin may influence photophosphorylation and reactions coupled with it is discussed.