Relative binding affinities of chlorophylls in peridinin–chlorophyll–protein reconstituted with heterochlorophyllous mixtures
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Peridinin–chlorophyll–protein (PCP), containing differently absorbing chlorophyll derivatives, are good models with which to study energy transfer among monomeric chlorophylls (Chls) by both bulk and single-molecule spectroscopy. They can be obtained by reconstituting the N-terminal domain of the protein (N-PCP) with peridinin and chlorophyll mixtures. Upon dimerization of these “half-mers”, homo- and heterochlorophyllous complexes are generated, that correspond structurally to monomeric protomers of native PCP from Amphidinium carterae. Heterochlorophyllous complexes contain two different Chls in the two halves of the complete structure. Here, we report reconstitution of N-PCP with binary mixtures of Chl a, Chl b, and [3-acetyl]-Chl a. The ratios of the pigments were varied in the reconstitution mixture, and relative binding constants were determined from quantification of these pigments in the reconstituted PCPs. We find higher affinities for both Chl b and [3-acetyl]-Chl a than for the native pigment, Chl a.
KeywordsDinoflagellate Light-harvesting Peridinin–chlorophyll–protein Chlorophyll Binding affinity
N-terminal domain of PCP
Work was supported by the Deutsche Forschungsgemeinschaft, Bonn (SFB 533, projects A6 and B7). T.H.P.B. is indebted for financial support from Ludwig-Maximilians University, München. S.M. acknowledges a grant from the Alexander-von-Humboldt foundation, Bonn. Work was supported by Center for Integrated Protein Science Munich (CiPSM).
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