PHOSPHORYLATION CONTROLS THE 3-DIMENSIONAL STRUCTURE OF PLANT LIGHT-HARVESTING COMPLEX-II

The most abundant chlorophyll-binding complex in plants is the intrins ic membrane protein light-harvesting complex II (LHC II), LHC II acts as a light-harvesting antenna and has an important role in the distrib ution of absorbed energy between the two photosystems of photosynthesi s. We used spectroscopic techniques to study a synthetic peptide with identical sequence to the LHC IIb N terminus found in pea, with and wi thout the phosphorylated Thr at the 5th amino acid residue, and to stu dy both forms of the native full-length protein, Our results show that the N terminus of LHC II changes structure upon phosphorylation and t hat the structural change resembles that of rabbit glycogen phosphoryl ase, one of the few phosphoproteins where both phosphorylated and non- phosphorylated structures have been solved. Our results indicate that phosphorylation of membrane proteins may regulate their function throu gh structural protein-protein interactions in surface-exposed domains.