Department of Chemistry, Southern Methodist University, Dallas, TX 75275.
Center for Drug Discovery, Design, and Delivery, Southern Methodist University, Dallas, TX 75275.
Proc Natl Acad Sci U S A. 2019 Sep 24;116(39):19449-19457. doi: 10.1073/pnas.1907875116. Epub 2019 Sep 4.
Computational and biochemical studies implicate the blue-light sensor cryptochrome (CRY) as an endogenous light-dependent magnetosensor enabling migratory birds to navigate using the Earth's magnetic field. Validation of such a mechanism has been hampered by the absence of structures of vertebrate CRYs that have functional photochemistry. Here we present crystal structures of (pigeon) CRY4 that reveal evolutionarily conserved modifications to a sequence of Trp residues (Trp-triad) required for CRY photoreduction. In CRY4, the Trp-triad chain is extended to include a fourth Trp (W369) and a Tyr (Y319) residue at the protein surface that imparts an unusually high quantum yield of photoreduction. These results are consistent with observations of night migratory behavior in animals at low light levels and could have implications for photochemical pathways allowing magnetosensing.
计算和生化研究表明，蓝光传感器隐花色素（CRY）是一种内源性的光依赖性磁传感器，使候鸟能够利用地球磁场进行导航。然而，由于缺乏具有功能光化学性质的脊椎动物 CRY 的结构，这种机制的验证一直受到阻碍。在这里，我们展示了 （鸽子）CRY4 的晶体结构，揭示了 CRY 光还原所需的 Trp 残基（Trp-三联体）序列的进化保守修饰。在 CRY4 中，Trp-三联体链延伸，包括蛋白质表面的第四个 Trp（W369）和 Tyr（Y319）残基，赋予了异常高的光还原量子产率。这些结果与在低光照水平下动物夜间迁徙行为的观察结果一致，并且可能对允许磁感觉的光化学途径有影响。
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