Shutova T, Villarejo A, Zietz B, Klimov V, Gillbro T, Samuelsson G, Renger G
Comparative studies on the properties of the extrinsic manganese-stabilizing protein from higher plants and of a synthetic peptide of its C-terminus
Biochimica Et Biophysica Acta-Bioenergetics: 2003 1604:95-104
The present study describes a comparative analysis on the fluorescence properties of the manganese-stabilizing protein (MSP), a synthetic peptide corresponding to its C terminus and a 7:1 (molar ratio) mixture of N-acetyl-tyrosine and N-acetyl-tryptophan, respectively, together with reconstitution experiments of oxygen evolution in MSP-depleted photosystem II (PS II) membrane fragments. It is found: (i) at neutral pH, the fluorescence from Trp(241) is strongly diminished in MSP solutions, whereas it highly dominates the overall emission from the C-terminus peptide, (ii) at alkaline pH, the emission of Tyr and Trp is quenched in both, MSP and C-terminus peptide, with increasing pH but the decline curve is shifted by about two pH units towards the alkaline region in MSP, (iii) a drastically different pattern emerges in the 7:1 mixture where the Trp emission even slightly increases at high pH, (iv) the anisotropy of the fluorescence emission is wavelength-independent (310-395 nm) and indicative of one emitter type (Trp) in the C-terminus peptide and of two emitter types (Tyr, Trp) in MSP, and (v) in MSP-depleted PS H membrane fragments the oxygen evolution is restored (up to 85% of untreated control) by rebinding of MSP but not by the C-terminus peptide, however, the presence of the latter diminishes the restoration effect of MSP. A quenching mechanism of Trp fluorescence by a next neighbored tyrosinate in the peptide chain is proposed and the relevance of the C terminus of MSP briefly discussed. (C) 2003 Elsevier Science B.V. All rights reserved.
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