The azido[14C]atrazine photoaffinity technique labels a 34‐kDa protein in Scenedesmus which functions on the oxidizing side of photosystem II

We have used azido[14C]atrazine to photoaffinity label thylakoids from wild‐type (WT) Scenedesmus and a mutant, LF‐1, which is blocked on the oxidizing side of photosystem II (PS II). One protein is labeled in each case, at 34 kDa in the WT and 36 kDa in LF‐1. Previous comparison of the WT with LF‐1 had been used to assign a PS II donor side function to the 34‐kDa protein. These results suggest that this photoaffinity technique does not label the herbicide‐binding protein involved in electron transfer on the reducing side of PS II.