The Antimycin-binding Site of Thylakoid Membranes from Chloroplasts

Abstract

Antimycin is a specific inhibitor of the electron-transport pathway that drives cyclic photophosphorylation in chloroplasts. The specificity of this effect has led to the suggestion [ 1 ] that the site of action is the putative enzyme ferredoxin-plastoquinone oxidoreductase (FQR), but this has not been positively identified. in mitochondria, antimycin acts on the cytochrome bc1 complex. Mills et al. [2] demonstrated the presence of a high-affinity binding site (Kd = 4 nm) in thylakoid membranes but the location of the site was not defined. Whether or not FQR is part of the cytochrome bf complex is uncertain [3].