Herbicide and Plastoquinone Binding to Photosystem II

Photoaffinity Label, Plastoquinone Depletion, Photosystem II Particles, Chlamydomonas In plastoquinone-depleted thylakoids “D C M U -type” herbicides generally have a lower binding affinity as compared to control thylakoids, with the exception o f DC M U itself. Contrary, binding properties of phenolic herbicides are not affected by plastoquinone depletion. DCM U 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 3 2 3 4 kDa protein, which seems to be different from another 3 2 -3 4 kDa protein which is preferentially labeled by a plastoquinoneazide.