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Photoactivation of the latent water‐oxidizing complex in photosystem II membranes isolated from dark‐grown spruce seedlings
Author(s) -
Kamachi Hiroyuki,
Tamura Noriaki,
Yoshihira Takashi,
Oku Tatsuo
Publication year - 1994
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1994.tb03015.x
Subject(s) - photosystem ii , membrane , chemistry , oxidizing agent , spinach , photosystem , photosynthesis , photochemistry , biophysics , biology , biochemistry , organic chemistry
Photosystem II membranes (D‐PSII) were isolated from dark‐grown spruce seedlings. All major PSII proteins except the 17‐ and 23‐kDa extrinsic proteins were present in D‐PSII. O 2 evolution and Mn content in D‐PSII were negligible, while PSII‐donor activity showed a value comparable to that of NH 2 OH‐treated PSII membranes (NH 2 OH‐L‐PSII) from light‐grown seedlings. Light incubation of D‐PSII with 1 m M MnCl 2 , 50 m M CaCl 2 and 100 μ M DCIP at pH 5.3 resulted in activation of the latent water‐oxidizing complex. Accomplishment of photoactivation of PSII membranes from dark‐grown spruce seedlings clearly indicates that only ligation of Mn 2+ to the apo‐water oxidizing complex is required for expression of O 2 evolution, and that protein synthesis is not involved in the photoactivation process. There was no essential difference between ‘photoactivation’ of naturally Mn‐free PSII membranes and ‘photoreactivation’ of artificially Mn‐depleted PSII membranes on kinetics, pH dependence, Mn 2+ ‐concentration dependence. However, kinetics and pH dependence of photoactivation were appreciably different in spruce PSII membranes and in PSII membranes of angiosperms such as wheat and spinach.