STRUCTURAL BASIS OF LIGHT-HARVESTING BY CAROTENOIDS - PERIDININ-CHLOROPHYLL-PROTEIN FROM AMPHIDINIUM-CARTERAE

Peridinin-chlorophyll-protein, a water-soluble light-harvesting comple x that has a blue-green absorbing carotenoid as its main pigment, is p resent in most photosynthetic dinoflagellates, Its high-resolution (2. 0 angstrom) x-ray structure reveals a noncrystallographic trimer in wh ich each polypeptide contains an unusual jellyroll fold of the alpha-h elical amino- and carboxyl-terminal domains, These domains constitute a scaffold with pseudo-twofold symmetry surrounding a hydrophobic cavi ty filled by two lipid, eight peridinin, and two chlorophyll a molecul es, The structural basis for efficient excitonic energy transfer from peridinin to chlorophyll is found in the clustering of peridinins arou nd the chlorophylls at van der Waals distances.