Probing the structure of photosystem II with amines and phenylhydrazine.
Photosynthetic oxygen evolution is catalyzed at the manganese-containing active site of photosystem II (PSII). Amines are analogs of substrate water and inhibitors of oxygen evolution. Recently, the covalent incorporation of (14)C from [(14)C]methylamine and benzylamine into PSII subunits has been demonstrated (Ouellette, A. J. A., Anderson, L. B., and Barry, B. A. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 2204-2209). To obtain more information concerning these labeling reactions, t-[(14)C]butylamine and phenylhydrazine were employed as probes. Neither compound can be oxidized by a transamination or addition/elimination mechanism, but both can react with activated carbonyl groups, produced as a result of posttranslational modification of amino acid residues, to give amine-derived adducts. (14)C incorporation into the PSII subunits D2/D1 and CP47 was obtained upon treatment of PSII with either t-[(14)C]butylamine or [(14)C]phenylhydrazine. For t-butylamine and methylamine, the amount of labeling increased when PSII was treated with denaturing agents. Labeling of CP47, D2, and D1 with methylamine and phenylhydrazine approached a one-to-one stoichiometry, assuming that D2 and D1 each have one binding site. Evidence was obtained suggesting that reductive stabilization and/or access are modulated by PSII light reactions. These results support the proposal that PSII subunits D2, D1, and CP47 contain quinocofactors and that access to these sites is sterically limited.
Anderson
L B
LB
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, St. Paul, Minnesota 55108, USA.
Ouellette
A J
AJ
Barry
B A
BA
D002250:Carbon Radioisotopes; D004591:Electrophoresis, Polyacrylamide Gel; D008027:Light; D008744:Methylamines / Q000737:chemistry* / Q000378:metabolism; D015335:Molecular Probes; D010659:Phenylhydrazines / Q000737:chemistry* / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000302:isolation & purification; D045332:Photosystem II Protein Complex; D011487:Protein Conformation; D011489:Protein Denaturation
D002250:Carbon Radioisotopes; D008744:Methylamines; D015335:Molecular Probes; D010659:Phenylhydrazines; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C030299:phenylhydrazine; C027451:methylamine