Protein-chromophore interactions in alpha-crustacyanin, the major blue carotenoprotein from the carapace of the lobster, Homarus gammarus. A study by 13C magic angle spinning NMR.
MAS (magic angle spinning) 13C NMR has been used to study protein-chromophore interactions in alpha-crustacyanin, the blue astaxanthin-binding carotenoprotein of the lobster, Homarus gammarus, reconstituted with astaxanthins labelled with 13C at the 14,14' or 15,15' positions. Two signals are seen for alpha-crustacyanin containing [14,14'-13C2]astaxanthin, shifted 6.9 and 4.0 ppm downfield from the 134.1 ppm signal of uncomplexed astaxanthin in the solid state. With alpha-crustacyanin containing [15,15'-13C2]astaxanthin, one essentially unshifted broad signal is seen. Hence binding to the protein causes a decrease in electronic charge density, providing the first experimental evidence that a charge redistribution mechanism contributes to the bathochromic shift of the astaxanthin in alpha-crustacyanin, in agreement with inferences based on resonance Raman data [Salares, et al. (1979) Biochim. Biophys. Acta 576, 176-191]. The splitting of the 14 and 14' signals provides evidence for asymmetric binding of each astaxanthin molecule by the protein.
Weesie
R J
RJ
Department of Biochemistry, University of Liverpool, UK.
Askin
D
D
Jansen
F J
FJ
de Groot
H J
HJ
Lugtenburg
J
J
Britton
G
G
D000818:Animals; D002338:Carotenoids / Q000737:chemistry*; D002352:Carrier Proteins; D009682:Magnetic Resonance Spectroscopy; D008121:Nephropidae / Q000737:chemistry; D010860:Pigments, Biological / Q000737:chemistry*; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D024341:Xanthophylls; D019207:beta Carotene / Q000031:analogs & derivatives*
D002352:Carrier Proteins; D010860:Pigments, Biological; D011506:Proteins; D024341:Xanthophylls; C018494:crustacyanins; D019207:beta Carotene; D002338:Carotenoids; C005948:astaxanthine