Involvement of the CP47 Protein in Stabilization and Photoactivation of a Functional Water-Oxidizing Complex in the Cyanobacterium Synechocystis sp. PCC 6803

Abstract

Oscillation patterns of the oxygen yield per flash induced by a train of single-turnover flashes were measured as a function of dark incubation and different pre-illumination conditions in several autotrophic mutant strains of Synechocystis sp. PCC 6803 carrying short deletions within the large, lumen-exposed hydrophilic region (loop E) of the chlorophyll a-binding photosystem II protein CP47. A physiological and biochemical characterization of these mutant strains has been presented previously [Eaton-Rye, J. J., & Vermaas, W. F. J. (1991) Plant Mol. Biol. 17, 1165-1177; Haag, E., Eaton-Rye, J. J., Renger, G., & Vermaas, W. F. J. (1993) Biochemistry 32, 4444-4454], and some functional properties were described recently [Gleiter, H. M., Haag, E., Shen, J.-R., Eaton-Rye, J. J., Inoue, Y., Vermaas, W. F. J., & Renger, G. (1994) Biochemistry 33, 12063-12071]. The present study shows that in several mutants the water-oxidizing complex (WOC) became inactivated during prolonged dark incubation, whereas the WOC of the wild-type strain remained active. The rate and extent of the inactivation in the mutants depend on the domain of loop E, where 3-8 amino acid residues were deleted. The most pronounced effects are observed in mutants delta(A373-D380) and delta(R384-V392). A competent WOC can be restored from the fully inactivated state by illumination with short saturating flashes. The number of flashes required for this process strongly depends on the site at which a deletion has been introduced into loop E. Again, the most prominent effects were found in mutants delta(A373-D380) and delta(R384-V392). Interestingly, the number of flashes required for activation was reduced by more than an order of magnitude in both mutants by the addition of 10 mM CaCl2 to the cell suspension. On the basis of a model for photoactivation proposed by Tamura and Cheniae (1987) [Biochim. Biophys. Acta 890, 179-194], a scheme is presented for the processes of dark inactivation and photoactivation in these mutants. The results presented here corroborate an important role of the large hydrophilic domain (loop E) of CP47 in a functional and stable WOC.

Supramolecular architecture of cyanobacterial thylakoid membranes: How is the phycobilisome connected with the photosystems?

“…The model also shows a vicinity of CP47 and the external 33 kDa protein which is supported by structural and functional data (Burnap and Sherman 1991; Gleiter et al 1995;Ohta et al 1995).…”

Is the manganese stabilizing 33 kDa protein of photosystem II attaining a ‘natively unfolded’ or ‘molten globule’ structure in solution?

“…Although site directed mutagenesis reveals that several amino acid residues of D1 and D2 are of functional and/or structural relevance in establishing a competent WOC [8–13], other polypeptides cannot be excluded as potential candidates for being essential constituents of the WOC. It was recently shown that the large lumen exposed loop E of the chlorophyll containing 47 kDa protein (CP47) is essential for the dark stability of the WOC [14–16] and the regulation of its chloride demand [17,18].…”

Oxygenic Photosynthesis

“…These polypeptides are also important in stabilising the reaction centre core and modify quinone binding. CP47, especially a sequence forming a large hydrophilic loop, is involved in stabilising the WOC [119].…”