Requirements for the phyotoactivation of the multimetric water-splitting enzyme in leaf segments following hydroxylamine induced inactivation
In weak yet optimal light intensities (30 ..mu..E.m/sup -2/.sec/sup -1/), the photoactivation of water oxidation in wheat (Triticum aestivum var. Oasis) leaf segments was obtained only after long (6-8h) dark preincubation. The complete photoactivation of O/sub 2/ evolution (..delta.. approx. 300 O/sub 2//Chl.h) required a coordinated and interdependent ligation of 4 Mn and reassembly of the 17, 23 kDa PSII polypeptides into the water oxidizing complex following initial release of these components by NH/sub 2/OH induced inactivation of the complex. Without dark preincubation, PSII was susceptible to a weak light photoinhibition process (t/sub 1/2/ approx. 2.5 min) that resulted maximally in 50% decrease in the quantum efficiency of PSII donor photooxidations and slower fluorescence rise measured in the presence of DCMU. Additional photoinhibition was not observed with either prolonged weak light illumination in the presence of translational inhibitors or 40-fold higher light intensity. However, in the absence of translational and photophosphorylation inhibitors both O/sub 2/ evolution and quantum efficiency of PSII donor photooxidations recovered from the photoinhibited state. Synthesis of two thylakoid membrane polypeptides was enhanced specifically during the light dependent recovery from the photoinhibited state. One of these polypeptides was identified as the herbicide-binding Q/sub B/ protein. Its synthesis seemed unrelated to the recovery from photoinhibition since maximal photoinhibition in the absence of protein synthesis altered neither the abundance of (/sup 35/S) labeled Q/sub B/ protein nor the (/sup 14/C) atrazine binding properties of isolated chloroplasts.
- Research Organization:
- Kentucky Univ., Lexington (USA)
- OSTI ID:
- 5806400
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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[Formation/stabilization of the water oxidizing complex: Polypeptide/secondary donor requirement]
[Formation/stabilization of the water oxidizing complex: Polypeptide/secondary donor requirement]. Progress report
Related Subjects
14 SOLAR ENERGY
PHOTOSYNTHETIC REACTION CENTERS
BIOCHEMICAL REACTION KINETICS
POLYPEPTIDES
BIOSYNTHESIS
CARBON 14 COMPOUNDS
CHLOROPLASTS
ENZYMES
HYDROXYLAMINE
LEAVES
OXYGEN
PHOTOSYNTHESIS
SULFUR 35
TRACER TECHNIQUES
VISIBLE RADIATION
WATER
AMINES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CELL CONSTITUENTS
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
ELECTROMAGNETIC RADIATION
ELEMENTS
EVEN-ODD NUCLEI
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
NONMETALS
NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PEPTIDES
PHOTOCHEMICAL REACTIONS
PROTEINS
RADIATIONS
RADIOISOTOPES
REACTION KINETICS
SULFUR ISOTOPES
SYNTHESIS
550201* - Biochemistry- Tracer Techniques
140505 - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)