摘　要：隐（花）色素（Cry）是一类具有调控基因表达及生物节律功能的黄素蛋白，其与光修复酶（photolyase）具有高度同源性。果蝇隐（花）色素（dCry）属于动物I型隐（花）色素，在果蝇生物钟系统中起到光受体的作用。在结构上，dCry蛋白包含N末端光修复酶同源区以及C末端尾巴结构。dCry的光修复酶同源区可以结合黄素腺嘌呤二核苷酸（FAD）辅酶，并且存在色氨酸（Trp）三（四）联体的电子传递路径。dCry的C末端尾巴结构可以通过类似底物结合光修复酶的方式结合到dCry的光修复酶同源区中的口袋结构上。在光照条件下，dCry结合的FAD辅酶可接受经Trp三（四）联体传递的电子，从而被光还原。然后，C末端尾巴可能从口袋结构中弹出，使dCry构象变化，进而通过蛋白的相互作用向下游传递信号。目前关于dCry光感受的机理及其信号状态学术界尚有争论。有观点认为，氧化型dCry经光还原后形成的阴离子自由基型是信号激活状态；而另一种观点则认为，dCry中阴离子自由基型FAD为基态，在光作用下进一步形成的激发状态才是信号激活状态，才能导致构象变化。而作用光谱的研究则揭示了dCry的信号激活状态可能并不局限于FAD的光还原作用，且不同波长的光对dCry的影响不同。本文将对dCry蛋白在果蝇生物钟系统中的功能及其结构特性进行介绍，并综述光感受机理和信号状态的研究进展，为深入研究dCry的生理功能和作用机理提供理论参考。
关键词：果蝇隐（花）色素；黄素蛋白；生物钟；光感受；作用光谱

Abstract: Cryptochrome (Cry) is a flavoprotein that regulates gene expression and entrains circadian rhythms. It has a high degree of homology with the photolyase. Drosophila cryptochrome (dCry) is type I animal Cry. It functions as a photoreceptor in Drosophila circadian clock. In structure, dCry contains a photolyase homology region at N terminal, and a C-terminal tail. The photolyase homology region binds an flavin adenine dinucleotide (FAD) cofactor, and has an electron transfer pathway consisting of a tryptophan triad (or tetrad). The C-terminal tail of dCry binds to a pocket structure at the photolyase homology region, in a manner resembling that substrate binds to photolyase. Under illumination, the bound FAD cofactor can accept an electron transferred by the tryptophan triad (or tetrad), and be photoreduced. Then, the C-terminal tail may eject from the pocket structure, leading to the conformational changes of dCry, and signal is transmitted to downstream by protein interaction. Hitherto, the mechanism of photoreception and signaling state of dCry are still controversial. In one model, the oxidized state of dCry is converted to the anion radical state upon photoreduction, which is the possible signaling state of dCry; in the alternative mode, dCry contains FAD•– in the ground state, the excitation of FAD•– by light to FAD•–* causes the conformational change, which is responsible for signaling. Nevertheless, the experiments on action spectrum of dCry revealed that signaling state of dCry may not be restricted with the photoreduction of FAD, and lights at different wavelengths may have different effects on dCry. Here, the functions of dCry in the entrainment of circadian clock and its structural features are reviewed, as well as the possible photoreception mechanisms and the signaling states of it, to provide theoretical reference for further exploration on the physiological functions and action mechanisms of dCry.
Key words: Drosophila cryptochrome; flavoprotein; circadian clock; photoreception; action spectrum