A. Sokolenko et al., THE 64 KDA POLYPEPTIDE OF SPINACH MAY NOT BE THE LHCII KINASE, BUT A LUMEN-LOCATED POLYPHENOL OXIDASE, FEBS letters, 371(2), 1995, pp. 176-180
Phosphorylation of chlorophyll alb-binding proteins of the of photosys
tem II light-harvesting assembly controls the energy distribution betw
een the two photosystems as well as the turnover of thylakoid membrane
proteins, The LHCII kinase, suggested to be a 64 kDa protein, is ligh
t-regulated by a mechanism involving reduction of plastoquinone and th
e participation of the cytochrome b(6)/f complex, A cDNA encoding that
protein has been isolated from a lambda gt11-based library made from
spinach polyadenylated RNA using a two-step strategy involving screeni
ng by polyclonal monospecific antisera and plaque hybridization, The p
rotein of 73.1 kDa molecular mass represents a precursor which contain
s a bipartite transit peptide of 101 amino acid residues (11.0 kDa) th
at directs the protein into the thylakoid lumen, It can be phosphoryla
ted in vitro, and exhibits significant homology to plant polyphenol ox
idases, not to kinases, The gene was therefore designated PpoA, Reinve
stigation of components in the molecular mass range of 50-70 kDa discl
osed five additional proteins which can accompany kinase-active cytoch
rome b(6)/f, photosystem II and AMS [1] preparations. Four Of them can
be phosphorylated in vitro; two with apparent molecular masses of 53
and 66 kDa are capable of phosphorylation, and represent new, yet unid
entified proteins.