Evidence for a dual function of the herbicide-binding D1 protein in photosystem II

AbstractThe LF-1 mutant of the green alga Scenedesmus obliquus is completely blocked on the oxidizing (water-splitting) side of photosystem II (PS II) while the reaction center and reducing side remain functional. A 34-kDa protein found in the PS II reaction center core complex of wild-type cells is replaced by a 36-kDa protein in the mutant cells. Both of these proteins are labeled by azido[14C]atrazine and are recognized by polyclonal antibodies raised against the herbicide-binding, D1 protein of Amaranthus hybridus. The data provide a new perspective on the role of the D1 protein by implying that it affects the oxidizing side of PS II in addition to performing its well established function on the reducing side