Functional characterization of mutant strains of the cyanobacterium Synechocystis sp. PCC 6803 lacking short domains within the large, lumen-exposed loop of the chlorophyll protein CP47 in photosystem II.
Several autotrophic mutant strains of Synechocystis sp. PCC 6803 carrying short deletions or a single-site mutation within the large, lumen-exposed loop (loop E) of the chlorophyll a-binding photosystem II core protein, CP47, are analyzed for their functional properties by measuring the flash-induced pattern of thermoluminescence, oxygen yield, and fluorescence quantum yield. A physiological and biochemical characterization of these mutant strains has been given in two previous reports [Eaton-Rye, J.J., & Vermaas, W.F.J. (1991) Plant Mol. Biol. 17, 1165-1177; Haag, E., Eaton-Rye, J.J., Renger, G., & Vermaas, S. F.J. (1993) Biochemistry 32, 4444-4454]. The results of the present study show that deletion of charged and conserved amino acids in a region roughly located between residues 370 and 390 decreases the binding affinity of the extrinsic PS II-O protein to photosystem II. Marked differences with PSII-O deletion mutants are observed with respect to Ca2+ requirement and the flash-induced pattern of oxygen evolution. Under conditions where a sufficient light activation is provided, the psbB mutants assayed in this study reveal normal S-state parameters and lifetimes. The results bear two basic implications: (i) the manganese involved in water oxidation can still be bound in a functionally normal or only slightly distorted manner, and (ii) the binding of the extrinsic PS II-O protein to photosystem II is impaired in mutants carrying a deletion in the domain between residues 370 and 390, but the presence of the PS II-O protein is still of functional relevance for the PS II complex, e.g., for maintenance of a high-affinity binding site for Ca2+ and/or involvement during the process of photoactivation.
Gleiter
H M
HM
Max-Volmer Institute for Physical and Biophysical Chemistry, Technical University Berlin, Germany.
Haag
E
E
Shen
J R
JR
Eaton-Rye
J J
JJ
Inoue
Y
Y
Vermaas
W F
WF
Renger
G
G
D001665:Binding Sites; D002734:Chlorophyll / Q000737:chemistry*; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005453:Fluorescence; D015151:Immunoblotting; D045342:Light-Harvesting Protein Complexes; D008163:Luminescent Measurements; D016296:Mutagenesis / Q000235:genetics; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism*; D045332:Photosystem II Protein Complex
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C070970:photosystem II, chlorophyll-binding protein, CP-47; D002734:Chlorophyll