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Discrete extraction of the Ca atom functional for O 2 evolution in higher plant photosystem II by a simple low pH treatment
Author(s) -
Ono Taka-aki,
Inoue Yorinao
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)80886-x
Subject(s) - spinach , photosystem ii , chemistry , membrane , photosynthetic reaction centre , extraction (chemistry) , biochemistry , photosynthesis , chromatography
Treatment of spinach PS II membranes with a citrate solution at pH 3.0 totally inactivated O 2 evolution concomitant with a 50% decrease in Ca abundance. Notably, neither the abundance of Mn and extrinsic proteins nor the activity of DPC photooxidation was at all affected by the treatment. The treated membranes evolved O 2 at a high rate in the presence of exogenous Ca 2+ , but the activity was sensitive to EDTA. However, when the treated membranes were incubated with Ca 2+ for a few tens of minutes, the O 2 ‐evolving activity became EDTA‐resistant, suggesting a firm re‐ligation of Ca 2+ to the Ca‐binding site. It was indicated that spinach PS II contains two Ca atoms per reaction center, and that the low pH citrate treatment selectively removes one of the two Ca atoms that is specifically functional for O 2 evolution, even in the presence of all three extrinsic proteins.