title: Identification, characterization, and resolution of the in vivo phosphorylated form of the D1 photosystem II reaction center protein.
abstract: The chloroplast-encoded D1 protein of oxygenic photosynthetic organisms is a component of the photosystem II reaction center. Previously, we detected an electrophoretic variant of D1 which was generated in vivo in granal-localized reaction centers in a light dependent manner (Callahan, F.E., Ghirardi, M.L., Sopory, S.K., Mehta, A.M., Edelman, M., and Mattoo, A.K. (1990) J. Biol. Chem. 265, 15357-15360). In the present study, we identify this modified form as phosphorylated D1. The in vivo phosphorylation occurs on a threonine residue(s) localized within 1 kDa from the N terminus and is identical to the phosphorylation of D1 catalyzed in vitro by a redox-regulated thylakoid-bound protein kinase. While virtually all of the D1 protein present in thylakoids can be phosphorylated in vitro, the steady-state level of phosphorylated D1 in vivo varies with light intensity and did not exceed 20% of the total D1 under the conditions of this study.
authors.affiliation: Plant Molecular Biology Laboratory, Beltsville Agricultural Research Center-West, United States Department of Agriculture, Maryland 20705.
authors.forename: T D
authors.initials: TD
authors.lastname: Elich
authors.forename: M
authors.initials: M
authors.lastname: Edelman
authors.forename: A K
authors.initials: AK
authors.lastname: Mattoo
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000596:Amino Acids / Q000032:analysis; D003624:Darkness; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D008027:Light; D008970:Molecular Weight; D015388:Organelles / Q000378:metabolism; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000302:isolation & purification; D010766:Phosphorylation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000302:isolation & purification / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D010944:Plants / Q000378:metabolism*; D014357:Trypsin
chemical_list: D000596:Amino Acids; D010748:Phosphopeptides; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D000255:Adenosine Triphosphate; D014357:Trypsin