Magnetoreception through Cryptochrome May Involve Superoxide
Magnetoreception through Cryptochrome May Involve Superoxide
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DOI：
10.1016/j.bpj.2009.03.048
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发表时间：
2009-06-17
影响因子：
3.4
通讯作者：
Schulten, Klaus
中科院分区：
文献类型：
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作者：
Solov'yov, Ilia A.;Schulten, Klaus
在过去的几十年里，已经证明许多动物物种在地球磁场中定位。研究得最好的例子之一是候鸟利用地磁场进行定向和导航。然而，动物磁感受的生物物理机制仍然不清楚。一种鸟类磁感受的理论援引了所谓的根对模型。这种机制涉及一对反应性自由基，其化学命运可以通过塞曼和超精细相互作用受到相对于地球磁场的方向的影响。地磁场很弱，也就是说，类似于0.5G，对可以建立磁罗盘感测的径向对施加了严格的限制。对于重定向地磁场中反应产率的显著变化，超精细相互作用必须与地球场塞曼相互作用一样弱，即，对有机化合物来说异常微弱这种弱的超精细相互作用可以实现，如果自由基之一是完全没有这种相互作用，实现在一个自由基对包含一个氧分子作为自由基之一。因此，我们在这里研究了感光体隐花色素中可能的基于自由基对的反应，该反应通过超氧自由基O-2（中心点-）将蛋白质的黄素基团从其信号状态FADH（中心点）减少到非活性状态FADH（-）（其与同样非活性的FAD反应）。我们认为，所建议的反应中的自旋动力学可以充当地磁指南针，并且非常低的生理浓度（nM-mu M）的其他有毒O-2（中心点-）对于生物功能来说是足够的，甚至是有利的。
In the last decades, it has been demonstrated that many animal species orient in the Earth magnetic field. One of the best-studied examples is the use of the geomagnetic field by migratory birds for orientation and navigation. However, the biophysical mechanism underlying animal magnetoreception is still not understood. One theory for magnetoreception in birds invokes the so-called radical-pair model. This mechanism involves a pair of reactive radicals, whose chemical fate can be influenced by the orientation with respect to the magnetic field of the Earth through Zeeman and hyperfine interactions. The fact that the geomagnetic field is weak, i.e., similar to 0.5 G, puts a severe constraint on the radical pair that can establish the magnetic compass sense. For a noticeable change of the reaction yield in a redirected geomagnetic field, the hyperfine interaction has to be as weak as the Earth field Zeeman interaction, i.e., unusually weak for an organic compound. Such weak hyperfine interaction can be achieved if one of the radicals is completely devoid of this interaction as realized in a radical pair containing an oxygen molecule as one of the radicals. Accordingly, we investigate here a possible radical pair-based reaction in the photoreceptor cryptochrome that reduces the protein's flavin group from its signaling state FADH(center dot) to the inactive state FADH(-) (which reacts to the likewise inactive FAD) by means of the superoxide radical, O-2(center dot-). We argue that the spin dynamics in the suggested reaction can act as a geomagnetic compass and that the very low physiological concentration (nM-mu M) of otherwise toxic O-2(center dot-) is sufficient, even favorable, for the biological function.