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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Direct observation of photolysis-induced tertiary structural changes in hemoglobin
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Direct observation of photolysis-induced tertiary structural changes in hemoglobin

机译：直接观察光解引起的血红蛋白三级结构变化

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摘要

Human Hb, an alpha(2)beta(2) tetrameric oxygen transport protein that switches from a T (tense) to an R (relaxed) quaternary structure during oxygenation, has long served as a model for studying protein allostery, in general. Time-resolved spectroscopic measurements after photodissociation of CO-liganded Hb have played a central role in exploring both protein dynamical responses and molecular cooperativity, but the direct visualization and the structural consequences of photodeligation have not yet been reported. Here we present an x-ray study of structural changes induced by photodissociation of half-liganded T-state and fully liganded R-state human Hb at cryogenic temperatures (25-35 K). On photodissociation of CO, structural changes involving the heme and the F-helix are more marked in the a subunit than in the beta subunit, and more subtle in the R state than in the T state. Photodeligation causes a significant sliding motion of the T-state beta heme. Our results establish that the structural basis of the low affinity of the T state is radically different between the subunits, because of differences in the packing and chemical tension at the hemes. [References: 44]
机译：人类Hb是一种在氧合过程中从T（紧张）转变为R（松弛）四级结构的α（2）beta（2）四聚体氧转运蛋白，长期以来一直用作研究蛋白质变构的模型。 CO配位的Hb光解离后的时间分辨光谱测量在探索蛋白质动力学响应和分子协同性方面起着中心作用，但是尚未报道光聚合的直接可视化和结构后果。在这里，我们介绍了在低温（25-35 K）下半配体T型态和完全配体R型人Hb光解引起的结构变化的X射线研究。关于CO的光解离，涉及血红素和F-螺旋的结构变化在a亚基中比在β亚基中更明显，在R状态中比在T状态中更微妙。光合作用引起T状态β血红素的明显滑动。我们的结果表明，由于血红素的堆积和化学张力的差异，亚基之间T态低亲和力的结构基础是根本不同的。 [参考：44]

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