Herbicide and Plastoquinone Binding to Photosystem II

Abstract

In plastoquinone-depleted thylakoids “DCMU-type” herbicides generally have a lower binding affinity as compared to control thylakoids, with the exception of DCMU itself. Contrary, binding properties of phenolic herbicides are not affected by plastoquinone depletion. DCMU in plastoquinone-depleted thylakoids can be displaced from the membrane by various substituted 1,4-benzoquinones, including plastoquinone-1. Labeling patterns by azido-atrazine are compared for thylakoids, plastoquinone-depleted thylakoids, and different photosystem II preparations from spinach and Chlamydomonas. Azido-atrazine tags a 32-34 kDa protein, which seems to be different from another 32-34 kDa protein which is preferentially labeled by a plastoquinone-azide.