Protein‐chromophore interactions in α‐crustacyanin, the major blue carotenoprotein from the carapace of the lobster, Homarus gammarus a study by 13 C magic angle spinning NMR

• Published in: FEBS Letters
• Main Authors: Weesie, R.J, Askin, D, Jansen, F.J.H.M, de Groot, H.J.M, Lugtenburg, J, Britton, G
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1995
• Subjects: Homarus gammarus
• Online Access: http://dx.doi.org/10.1016/0014-5793(95)00191-b; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1016%2F0014-5793%2895%2900191-B; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1016%2F0014-5793(95)00191-B; https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2895%2900191-B

MAS (magic angle spinning) 13 C NMR has been used to study protein‐chromophore interactions in α‐crustacyanin, the blue astaxanthin‐binding carotenoprotein of the lobster, Homarus gammarus , reconstituted with astaxanthins labelled with 13 C at the 14,14′ or 15,15′ positions. Two signals are seen for α‐crustacyanin containing [14,14′‐ 13 C 2 ]astaxanthin, shifted 6.9 and 4.0 ppm downfield from the 134.1 ppm signal of uncomplexed astaxanthin in the solid state. With α‐crustacyanin containing [15,15′‐ 13 C 2 ]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 α‐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.