Anacystis nidulans demonstrates a photosystem II cation requirement satisfied only by Ca/sup 2 +/ or Na/sup +1/

Journal Article · Tue Oct 01 00:00:00 EDT 1985 · Plant Physiol.; (United States)

OSTI ID:6299769

Becker, D W; Brand, J J

Anacystis nidulans exhibits a total loss of photosystem II (PSII) activity upon incubation in a nutrient medium deficient in Ca/sup 2 +/ and Na/sup +/ and containing a divalent cation chelator. This loss of activity is light-dependent, which corresponds to an energy requirement. Likewise, Ca/sup 2 +/ efflux takes place only in cells incubated in light. The loss of PSII activity is reversible by addition of submillimolar amounts of either Ca/sup 2 +/ or Na/sup +/ to the external medium but not by the addition of any other cation. Restoration of lost PSII activity also requires light. Light saturation curves for partially depleted cells demonstrate both lower maximum O/sub 2/ evolution rates and decreased relative quantum yields when compared to control cells. Partial electron transport reactions isolate the site of the Ca/sup 2 +//Na/sup +/ effect to the reaction center itself or immediately on its oxidizing side and exclude the water-splitting complex. O/sub 2/ flash yields decline during cation depletion, indicating a decrease in the number of functional PSII reaction centers, but the maximum turnover rate for still functional reaction centers does not decline. Thus, PSII of A. nidulans exhibits an all-or-none cation requirement, satisfied only by Ca/sup 2 +/ or Na/sup +/.

• Research Organization: Univ. of Texas, Austin
• OSTI ID: 6299769
• Journal Information: Plant Physiol.; (United States), Vol. 79:2
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CALCIUM COMPOUNDS
BIOCHEMICAL REACTION KINETICS
PHOTOSYNTHETIC REACTION CENTERS
PHOTOCHEMISTRY
SODIUM COMPOUNDS
CATIONS
PHOTOSYNTHETIC BACTERIA
PHOTOSYNTHETIC MEMBRANES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CHARGED PARTICLES
CHEMISTRY
IONS
KINETICS
MEMBRANES
REACTION KINETICS
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