Amine binding and oxidation at the catalytic site for photosynthetic water oxidation.
Photosynthetic water oxidation occurs at the Mn-containing catalytic site of photosystem II (PSII). By the use of 14C-labeled amines and SDS-denaturing PAGE, covalent adducts derived from primary amines and the PSII subunits, CP47, D2/D1, and the Mn-stabilizing protein, can be observed. When PSII contains the 18- and 24-kDa extrinsic proteins, which restrict access to the active site, no 14C labeling is obtained. NaCl, but not Na2SO4, competes with 14C labeling in Mn-containing PSII preparations, and the concentration dependence of this competition parallels the activation of oxygen evolution. Formation of 14C-labeled adducts is observed in the presence or in the absence of a functional manganese cluster. However, no significant Cl- effect on 14C labeling is observed in the absence of the Mn cluster. Isolation and quantitation of the 14C-labeled aldehyde product, produced from [14C]benzylamine, gives yields of 1. 8 +/- 0.3 mol/mol PSII and 2.9 +/- 0.2 mol/mol in Mn-containing and Mn-depleted PSII, respectively. The corresponding specific activities are 0.40 +/- 0.07 micromol(micromol PSII-hr)-1 and 0.64 +/- 0.04 micromol(micromol PSII-hr)-1. Cl- suppresses the production of [14C]benzaldehyde in Mn-containing PSII, but does not suppress the production in Mn-depleted preparations. Control experiments show that these oxidation reactions do not involve the redox-active tyrosines, D and Z. Our results suggest the presence of one or more activated carbonyl groups in protein subunits that form the active site of PSII.
Ouellette
A J
AJ
Department of Biochemistry, University of Minnesota, St. Paul, MN 55108, USA.
Anderson
L B
LB
Barry
B A
BA
D006631:Amine Oxidase (Copper-Containing); D000588:Amines / Q000378:metabolism*; D000818:Animals; D001547:Benzaldehydes / Q000032:analysis; D001596:Benzylamines / Q000378:metabolism*; D001665:Binding Sites; D002384:Catalysis; D002417:Cattle; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes; D010084:Oxidation-Reduction; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000097:blood*; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D045332:Photosystem II Protein Complex
D000588:Amines; D001547:Benzaldehydes; D001596:Benzylamines; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C070970:photosystem II, chlorophyll-binding protein, CP-47; C030796:benzylamine; D006631:Amine Oxidase (Copper-Containing); D000587:Oxidoreductases Acting on CH-NH Group Donors; C032175:benzaldehyde