Energy transduction on the nanosecond time scale: Early structural events in a xanthopsin photocycle
Energy transduction on the nanosecond time scale: Early structural events in a xanthopsin photocycle
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DOI：
10.1126/science.279.5358.1946
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发表时间：
1998-03-20
期刊：
影响因子：
56.9
通讯作者：
Moffat, K
中科院分区：
文献类型：
--
作者：
Perman, B;Srajer, V;Moffat, K
光活性黄蛋白（PYP）是真细菌蓝光光感受器黄嘌呤家族的一员。在吸收光后，PYP进入光循环，最终将光信号中包含的能量转换为改变的生物响应。纳秒时间分辨x射线晶体学用于确定PYP的发色团在吸收光的光电子激发后1纳秒内形成的短暂红移中间态[pR]的结构。所得到的结构模型表明，[pR]态具有4-羟基肉桂硫酯发色团的顺式构象，并且反式到顺式异构化的过程伴随着新的氢键的形成，这些氢键取代了在发色团激发时断裂的氢键。组成发色团结合袋的柔韧性区域有助于降低暗态（表示为pG和[pR]）之间的活化能垒，并有助于启动进入光循环。为光能转导的初始过程，最终转化为生理信号提供了直接的结构证据。
Photoactive yellow protein (PYP) is a member of the xanthopsin family of eubacterial blue-light photoreceptors. On absorption of light, PYP enters a photocycle that ultimately transduces the energy contained in a light signal into an altered biological response, Nanosecond time-resolved x-ray crystallography was used to determine the structure of the short-lived, red-shifted, intermediate state denoted [pR], which develops within 1 nanosecond after photoelectronic excitation of the chromophore of PYP by absorption of light. The resulting structural model demonstrates that the [pR] state possesses the cis conformation of the 4-hydroxyl cinnamic thioester chromophore, and that the process of trans to cis isomerization is accompanied by the specific formation of new hydrogen bonds that replace those broken upon excitation of the chromophore. Regions of flexibility that compose the chromophore-binding pocket serve to lower the activation energy barrier between the dark state, denoted pG, and [pR], and help initiate entrance into the photocycle. Direct structural evidence is provided for the initial processes of transduction of light energy, which ultimately translate into a physiological signal.