Journal Article

Involvement of Carboxyl Groups of the PSII Reaction Center Proteins in Photoactivation of the Apo-Water-Oxidizing Complex

Noriaki Tamura, Kosaku Noda, Kunimitsu Wakamatsu, Hiroyuki Kamachi, Hiroshi Inoue and Keishiro Wada

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 38, issue 5, pages 578-585
Published in print January 1997 | ISSN: 0032-0781
Published online January 1997 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029207
Involvement of Carboxyl Groups of the PSII Reaction Center Proteins in Photoactivation of the Apo-Water-Oxidizing Complex

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Involvement of residues of acidic amino acids in photo-ligation of manganese into the apo-water-oxidizing complex was investigated by use of l-ethyl-3-[3-(dimethylami-no)propyl]carbodiimide (EDC), a water-soluble carboxyl modifier. Treatment of Mn-depleted PSII membranes by EDC in the presence of nucleophiles induced a loss of photoactivation capability in the Mn complex and partial loss of capability of photooxidation of Mn2+, but little decrease in the DCIP photoreduction supported by diphen-ylcarbazide. The inhibition of diphenylcarbazide-photo-oxidation by submicromolar Mn2+, indicative of the intactness of high-affinity Mn-binding sites, was apparently abolished by EDC treatment. From amino acid quantitation analysis of Dl and D2 proteins and CP47 of the chemically-modified membranes, approximately three carboxyl groups of the D1 protein were found to be chemically-modified with EDC after removal of the functional Mn. These results suggest that acidic amino acids on the D1 protein are involved in photoactivation of the apo-water-oxidizing complex and probably in ligation of Mn to the water-oxidizing complex.

Keywords: Chemical modifier; Manganese; Oxygen evolution; Photoactivation; Photosystem; Spinach

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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