Zagalsky P F
Department of Molecular Biology and Biochemistry, Royal Holloway College, University of London, Egham, Surrey TW20 OEX, England.
Acta Crystallogr D Biol Crystallogr. 2003 Aug;59(Pt 8):1529-31. doi: 10.1107/s0907444903013416. Epub 2003 Jul 23.
The crystal structure of a beta-crustacyanin allows an analysis of the various proposals for the mechanism of the bathochromic shift from orange to purple-blue of astaxanthin in this lobster carotenoprotein. Structural and previous chemical and biophysical studies suggest that extension of conjugation by coplanarization of the beta-ionone rings with the polyene chain and polarization resulting from hydrogen bonding at the C(4) and C(4') keto groups may be mainly responsible for the bathochromic shift. Additional contributions may arise from medium effects and possibly from bowing of the polyene chain on binding. Previous biophysical data revealing a somewhat symmetrical polarization of astaxanthin in crustacyanin are thereby also accounted for. A puzzling feature remains unexplained: the bathochromic shifts, larger than that of astaxanthin, shown by some cyclopentenedione carotenoids in reconstituted carotenoproteins. This mini review enlarges on the original analysis and conclusions of Cianci et al. [(2002), Proc. Natl Acad. Sci. USA, 99, 9795-9800].
β-甲壳蓝蛋白的晶体结构有助于分析关于这种龙虾类胡萝卜素蛋白中虾青素从橙色到紫蓝色红移机制的各种提议。结构研究以及之前的化学和生物物理研究表明，β-紫罗兰酮环与多烯链共平面化导致的共轭延伸以及C(4)和C(4')酮基处氢键作用产生的极化可能是红移的主要原因。介质效应以及多烯链在结合时可能的弯曲也可能有额外贡献。之前揭示虾青素在甲壳蓝蛋白中存在某种对称极化的生物物理数据也因此得到了解释。一个令人困惑的特征仍然无法解释：一些环戊二烯酮类胡萝卜素在重组类胡萝卜素蛋白中显示出比虾青素更大的红移。这篇小型综述扩展了Cianci等人[(2002年)，《美国国家科学院院刊》，99，9795 - 9800]的原始分析和结论。
