Studies on the light-induced loss of the D1 protein in photosystem-II membrane fragments.

PS II membrane fragments produced from higher plant thylakoids by Triton X-100 treatment exhibit strong photoinhibition and concomitant fast degradation of the D1 protein. Involvement of (molecular) oxygen is necessary for degradation of the D1 protein.The herbicides atrazine and diuron, but not ioxynil, partly protect the D1 protein against degradation. Binding of atrazine to the D1 protein is necessary to protect the D1 polypeptide, as shown with PS II membrane fragments from an atrazine-resistant biotype of Chenopodium album which are protected by diuron not by atrazine.