Light-dependent degradation of the D1 protein in photosystem II is accelerated after inhibition of the water splitting reaction

Journal Article · Tue Jul 03 00:00:00 EDT 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00478a010· OSTI ID:6143294

Jegerschoeld, C V; Virgin, I; Styring, S ^[1]

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1. Univ. of Stockholm (Sweden)

Strong illumination of oxygen-evolving organisms inhibits the electron transport through photosystem II (photoinhibition). In addition the illumination leads to a rapid turnover of the D1 protein in the reaction center of photosystem II. In this study the light-dependent degradation of the D1 reaction center protein and the light-dependent inhibition of electron-transport reactions have been studied in thylakoid membranes in which the oxygen evolution has been reversibly inhibited by Cl- depletion. The results show that Cl(-)-depleted thylakoid membranes are very vulnerable to damage induced by illumination. Both the D1 protein and the inhibition of the oxygen evolution are 15-20 times more sensitive to illumination than in control thylakoid membranes. The presence, during the illumination, of the herbicide 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) prevented both the light-dependent degradation of the D1 protein and the inhibition of the electron transport. The protection exerted by DCMU is seen only in Cl(-)-depleted thylakoid membranes. These observations lead to the proposal that continuous illumination of Cl(-)-depleted thylakoid membranes generates anomalously long-lived, highly oxidizing radicals on the oxidizing side of photosystem II, which are responsible for the light-induced protein damage and inhibition. The presence of DCMU during the illumination prevents the formation of these radicals, which explains the protective effects of the herbicide. It is also observed that in Cl(-)-depleted thylakoid membranes, oxygen evolution (measured after the readdition of Cl-) is inhibited before electron transfer from diphenylcarbazide to dichlorophenolindophenol.

• OSTI ID: 6143294
• Journal Information: Biochemistry; (USA), Vol. 29:26; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
HERBICIDES
BIOLOGICAL EFFECTS
PHOTOSYNTHETIC REACTION CENTERS
BIOCHEMISTRY
THYLAKOID MEMBRANE PROTEINS
METABOLISM
INHIBITION
OXYGEN
PHOTOSYNTHETIC MEMBRANES
RADICALS
VISIBLE RADIATION
CHEMISTRY
ELECTROMAGNETIC RADIATION
ELEMENTS
MEMBRANE PROTEINS
MEMBRANES
NONMETALS
ORGANIC COMPOUNDS
PESTICIDES
PROTEINS
RADIATIONS
550200* - Biochemistry