Twisting a ß-Carotene, an Adaptive Trick from Nature for Dissipating Energy during Photoprotection.
J Biol Chem
; 292(4): 1396-1403, 2017 01 27.
Article
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| MEDLINE
| ID: mdl-27994060
ABSTRACT
Cyanobacteria possess a family of one-helix high light-inducible proteins (Hlips) that are homologous to light-harvesting antenna of plants and algae. An Hlip protein, high light-inducible protein D (HliD) purified as a small complex with the Ycf39 protein is evaluated using resonance Raman spectroscopy. We show that the HliD binds two different ß-carotenes, each present in two non-equivalent binding pockets with different conformations, having their (0,0) absorption maxima at 489 and 522 nm, respectively. Both populations of ß-carotene molecules were in all-trans configuration and the absorption position of the farthest blue-shifted ß-carotene was attributed entirely to the polarizability of the environment in its binding pocket. In contrast, the absorption maximum of the red-shifted ß-carotene was attributed to two different factors the polarizability of the environment in its binding pocket and, more importantly, to the conformation of its ß-rings. This second ß-carotene has highly twisted ß-rings adopting a flat conformation, which implies that the effective conjugation length N is extended up to 10.5 modifying the energetic levels. This increase in N will also result in a lower S1 energy state, which may provide a permanent energy dissipation channel. Analysis of the carbonyl stretching region for chlorophyll a excitations indicates that the HliD binds six chlorophyll a molecules in five non-equivalent binding sites, with at least one chlorophyll a presenting a slight distortion to its macrocycle. The binding modes and conformations of HliD-bound pigments are discussed with respect to the known structures of LHCII and CP29.
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MEDLINE
Asunto principal:
Proteínas Bacterianas
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Beta Caroteno
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Complejos de Proteína Captadores de Luz
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Synechocystis
Idioma:
En
Revista:
J Biol Chem
Año:
2017
Tipo del documento:
Article