The S sub 0 state of photosystem II induced by hydroxylamine: Differences between the structure of the manganese complex in the S sub 0 and S sub 1 states determined by X-ray absorption spectroscopy

• Published in: Biochemistry (Easton) Vol. 29:2
• Main Authors: Guiles, R.D., Yachandra, V.K., McDermott, A.E., Cole, J.L., Dexheimer, S.L., Britt, R.D., Sauer, K., Klein, M.P.
• Format: Journal Article
• Language: English
• Published: United States 16-01-1990
• Subjects: ABSORPTION SPECTROSCOPY; AMIDES; AMINES; BIOLOGICAL EFFECTS; CARBONIC ACID DERIVATIVES; CHEMICAL REACTIONS; COMPLEXES; ELECTRON SPIN RESONANCE; FINE STRUCTURE; FOOD; HYDROGEN COMPOUNDS; HYDROXYLAMINE; MAGNETIC RESONANCE; MAGNOLIOPHYTA; MAGNOLIOPSIDA; MANGANESE COMPLEXES; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; OXIDATION; OXYGEN COMPOUNDS; PHOTOSYNTHETIC REACTION CENTERS; PLANTS; RADIOLOGY AND NUCLEAR MEDICINE; RESONANCE; SPECTROSCOPY; SPINACH; TRANSITION ELEMENT COMPLEXES; UREA; VEGETABLES 550602 > Medicine > External Radiation in Diagnostics > (1980-); WATER; X-RAY SPECTROSCOPY
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00454a024

Hydroxylamine at low concentrations causes a two-flash delay in the first delay in the first maximum flash yield oxygen evolved from spinach photosystem II (PSII) subchloroplast membranes that have been excited by a series of saturating flashes of light. Untreated PSII membrane preparations exhibit a multiline EPR signal assigned to a manganese cluster and associated with the S{sub 2} state when illuminated at 195 K, or at 273 K in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). The authors used the extent of suppression of the multiline EPR signal observed in samples illuminated at 195 K to determine the fraction of PSII reaction centers set back to a hydroxylamine-induced S{sub 0}-like state, which they designate S{sub 0}. The manganese K-edge X-ray absorption edges for dark-adapted PSII preparations with or without hydroxylamine are virtually identical. This indicates that, despite its high binding affinity to the oxygen-evolving complex (OEC) in the dark, hydroxylamine does not reduce chemically the manganese cluster within the OEC in the dark. After a single turnover of PSII a shift to lower energy is observed in the inflection of the Mn K-edge of the manganese cluster. They conclude that, in the presence of hydroxylamine, illumination causes a reduction of the OEC, resulting in a state resembling S{sub 0}. This lower Mn K-edge energy of S{sub 0}, relative to the edge of S{sub 1}, implies that storage and stabilization of an oxidative equivalent within the manganese cluster during the S{sub 0} {yields} S{sub 1} state transition. An analysis of the extended X-ray absorption fine structure (EXAFS) of the S{sub 0} state indicates that a significant structural rearrangement occurs between the S{sub 0} and S{sub 1} states.