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
Hm. Gleiter et al., 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, Biochemistry, 33(40), 1994, pp. 12063-12071
Several autotrophic mutant strains of Synechocystis sp. PCC 6803 carry
ing short deletions or a single-site mutation within the large, lumen-
exposed loop (loop E) of the chlorophyll a-binding photosytem II core
protein, CP47, are analyzed for their functional properties by measuri
ng the flash-induced pattern of thermoluminescence, oxygen yield, anti
fluorescence quantum yield. A physiological and biochemical character
ization of these mutant strains has been given in two previous reports
[Eaton-Rye, J. J., and Vermaas, W. F. J. (1991) Plant Mel. Biol. 17,
1165-1177; Haag, E., Eaten-Rye, J. J., Renger, G., and Vermaas, S. F.
J. (1993) Biochemistry 32, 4444-4454]. The results of the present stud
y show that deletion of charged and conserved amino acids in a region
roughly located between residues 370 and 390 decreases the binding aff
inity of the extrinsic PS II-O protein to photosystem II. Marked diffe
rences with PSII-O deletion mutants are observed with respect to Ca2requirement and the flash-induced pattern of oxygen evolution. Under c
onditions where a sufficient light activation is provided, the psbB mu
tants assayed in this study reveal normal S-state parameters and lifet
imes. The results bear two basic implications: (i) the manganese invol
ved in water oxidation can still be bound ina functionally normal or o
nly slightly distorted manner, and (ii) the binding of the extrinsic P
S II-O protein to photosystem II is impaired in mutants carrying a del
etion 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 com
plex, e.g., for maintenance of a high-affinity binding site for Ca2+ a
nd/or involvement during the process of photoactivation.