Chlorophyll b is involved in long-wavelength spectral properties of light-harvesting complexes LHC I and LHC II

Chlorophyll (Chl) molecules attached to plant light-harvesting complexes (LHC) differ in their spectral behavior. While most Chl a and Chl b molecules give rise to absorption bands between 645 nm and 670 nm, some special Chls absorb at wavelengths longer than 700 nm. Among the Chl alb-antennae of higher plants these are found exclusively in LHC I. In order to assign this special spectral property to one chlorophyll species we reconstituted LHC of both photosystem I (Lhca4) and photo-system II (Lhcb1) with carotenoids and only Chi fl or Chi 6 and analyzed the effect on pigment binding, absorption and fluorescence properties. In both LHCs the Chi-binding sites of the omitted Chi species were occupied bi the other species resulting in a constant total number of Chls in these complexes. 77-K spectroscopic measurements demonstrated that omission of Chi b in refolded Lhca4 resulted in a loss of long-wavelength absorption and 730-nm fluorescence emission, In Lhcb1 with only Chi h long-wavelength emission was presented. These results clearly demonstrate the involvement of Chi h in establishing long-wavelength properties. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.