Structural basis of light harvesting by carotenoids: Peridinin-chlorophyll-protein from Amphidinium carterae

Peridinin-chlorophyll-protein, a water-soluble light-harvesting complex that has a blue-green absorbing carotenoid as its main pigment, is present in most photosynthetic dinoflagellates, Its high-resolution (2.0 angstrom) x-ray structure reveals a noncrystallographic trimer in which each polypeptide contains an unusual jellyroll fold of the alpha-helical amino- and carboxyl-terminal domains, These domains constitute a scaffold with pseudo-twofold symmetry surrounding a hydrophobic cavity filled by two lipid, eight peridinin, and two chlorophyll a molecules, The structural basis for efficient excitonic energy transfer from peridinin to chlorophyll is found in the clustering of peridinins around the chlorophylls at van der Waals distances.