Destabilization by high pH of the S1‐state of the oxygen‐evolving complex in photosystem II particles

• Published in: FEBS letters 1986-01, Vol.195 (1-2), p.313-318
• Main Authors: Plijter, Johan J., de Groot, Alex, van Dijk, Minse A., van Gorkom, Hans J.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Cell structures and functions; Chl, chlorophyll; Chloroplast, photosynthetic membrane and photosynthesis; DCBQ, 2,5-dichloro-p-benzoquinone; DCMU, 3-(3',4'-di-chlorophenyl)-1,1-dimethylurea; Fundamental and applied biological sciences. Psychology; Mes, 4-morpholineethane sulfonic acid; Molecular and cellular biology; Oxygen-evolving complex S-state Photosystem II Manganese pH effect Destabilization; PS II, photosystem II; Tricine, N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(86)80184-3

The S‐state distribution in a dark‐adapted photosystem II preparation, isolated from spinach chloroplasts, can be changed by pH. The period 4 oscillation of the oxygen‐releasing reaction, as measured by UV absorbance changes, is shifted by one flash at pH 8.3. This is not due to the generation of the EPR signal II on the first flash, or to the loss of a positive charge to some other electron donor after the first flashes. It is concluded that at pH 8.3 the S1‐state is reduced to S0. The half‐time of the reduction of S1 to S0 is 45 s, and the reduction is reversed in the dark if the pH is readjusted to pH 6.0. The oxygen release at pH 8.3 is irreversibly slowed down to about 3.2 ms.