Molecular orientation of plastocyanin on spinach thylakoid membranes as determined by acetylation of lysine residues.
To reveal the molecular orientation of plastocyanin (PC) on spinach thylakoid membranes, the position of Lys residues modified by acetic anhydride was compared between thylakoid-bound PC and the isolated one. Digestion of the isolated PC by a trypsin yielded a peptide map with seven spots prior to the acetylation of the protein; none of the spots appeared after the isolated PC was acetylated. On the other hand, there were two spots on the peptide map of the PC acetylated when it was bound to the thylakoids. Those spots were revealed by their amino acid compositions to correspond to the peptide fragments Phe 82-Lys 95 and Val 96-Asn 99. Thus, the Lys residues 81 and 95 of the thylakoid-bound PC were not acetylated. These results suggest that the PC molecule binds to the thylakoids with a specific region including the Lys's 81 and 95 in contact with the membranes. The Lys's 81 and 95 are located near Tyr 83, which has been thought to be the delivery site of electrons from the Cu2+ center.
D000107:Acetylation; D000595:Amino Acid Sequence; D008239:Lysine / Q000032:analysis*; D008565:Membrane Proteins / Q000032:analysis*; D008566:Membranes / Q000032:analysis; D010940:Plant Proteins / Q000032:analysis*; D010944:Plants / Q000032:analysis / Q000648:ultrastructure; D010970:Plastocyanin / Q000032:analysis*; D011485:Protein Binding; D011487:Protein Conformation; D013499:Surface Properties
D008565:Membrane Proteins; D010940:Plant Proteins; C042085:thylakoid membrane phosphoprotein, plant; D010970:Plastocyanin; D008239:Lysine