Carotenoid-Protein Complexes
Abstract A survey of carotenoid-protein complexes is presented. Distinction is made between astaxanthin-proteins in which the absorption band of the carotenoid is unaltered in shape, and carotenoid-lipoglycoprotein complexes. The proposal by Buchwald and Jencks 79 that the carotenoid is twisted about the double bonds of the polyene chain, is discussed and sustained for astaxanthin-proteins. A mode of binding for the carotenoid in these complexes is proposed, involving hydrogen-bonding of keto groups of the polyene to imide groups of peptide bonds of the apoprotein.