Labeling quinone-binding sites in photosynthetic reaction centers: a 38-kilodalton protein associated with the acceptor side of photosystem II

Journal Article · Wed Apr 01 00:00:00 EST 1987 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.84.7.1774· OSTI ID:6061626

Worland, S T; Yamagishi, A; Isaacs, S; Sauer, K; Hearst, J E

2-Acetoxymethyl-1,4-naphthoquinone (2-AcOMeNQ) binds with rapid kinetics and high affinity to the primary quinone Q/sub A/ site of reaction centers from Rhodopseudomonas capsulata. Binding of 2-AcOMeNQ fully restores electron-transfer activity with kinetics that is similar, but not identical, to that seen with ubiquinone-50. When bound at the Q/sub A/ site, 2-AcOMeNQ preferentially labels the L subunit. This preference suggests that 2-AcOMeNQ labels primarily the region of a quinone-binding site that is close to the first isoprenoid unit of the side chain, which is expected from the location and structure of the reaction region of the molecule. In photosystem II particles from Synechococcus sp., 2-AcOMeNQ primarily labels two polypeptides with apparent molecular masses of 38 and 19 kDa. Labeling of only the 38-kDa polypeptide is sufficiently sensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) to conclude that it is involved in binding quinones on the acceptor side of photosystem II. Although the authors have not yet identified the 38-kDa protein, its properties suggest that it is the D2 protein. From the DCMU-sensitive labeling and from homologies to functionally important regions of the bacterial reaction-center subunits, they propose that the 38-kDa protein is intimately involved in binding the cofactors that mediate primary photochemistry.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6061626
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 84:7
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
PHOTOSYNTHETIC REACTION CENTERS
CONFIGURATION INTERACTION
PROTEINS
BIOCHEMISTRY
QUINONES
TRITIUM COMPOUNDS
BIOCHEMICAL REACTION KINETICS
ELECTRON TRANSFER
LIQUID COLUMN CHROMATOGRAPHY
RHODOPSEUDOMONAS
THIN-LAYER CHROMATOGRAPHY
AROMATICS
BACTERIA
CHEMISTRY
CHROMATOGRAPHY
KINETICS
LABELLED COMPOUNDS
MICROORGANISMS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
REACTION KINETICS
SEPARATION PROCESSES
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)