新功能、新界面、新体验,扫描即可下载生物谷APP!
首页 » Nature报道 » Nature:温度扫描低温晶体学揭示光敏色素的反应中间体

Nature:温度扫描低温晶体学揭示光敏色素的反应中间体

来源:生物谷 2011-11-18 22:51

光是调节生物体重要生理过程(如生物钟等)的一个基本信号。植物,真菌和细菌中含有很多光敏色素,形成了一系列红色光敏感的感光器。他们在红光吸收态(PR)和远红光吸收态(PFR)之间的经过可逆的光转化,从而将光信号最终转换成一个调解后续细胞反应的独特生物信号。

已有几种微生物光敏色素,在红光吸收态(PR)或远红光吸收态(PFR)的暗适应过程中的结构已确定。然而,最初的光化学事件的结构性质并没有被衍射分析表征。

在这里,我们报告了绿脓杆菌光敏色素的光化学反应中三个中间体的晶体结构。我们使用冷凝阱晶体捕捉中间体,然后扫描光化学反应进行时发生结构性的变化时的温度。绿脓杆菌光敏色素光诱导的构象变化起源于环胆绿素(BV)发光基团的D环,而C15=C16的环C和D之间双键连接的E-to-Z异构化触发最初的光化学事件。当发光基团松弛,C15次甲基桥的两个二面角的扭曲是相反的。结构变化会进一步扩展到A环和B环,及周围的蛋白质区域。这些数据表明,绿脓杆菌光敏色素在远红光吸收态(PFR)吸收一个光子,通过扭曲和解缆在密闭的蛋白质腔中的线性卟啉上的次甲基桥结构将光信号转换成光信号。(生物谷bioon.com)

doi:10.1038/nature10506
PMC:
PMID:

Temperature-scan cryocrystallography reveals reaction intermediates in bacteriophytochrome

Xiaojing Yang, Zhong Ren,Jane Kuk & Keith Moffat

Light is a fundamental signal that regulates important physiological processes such as development and circadian rhythm in living organisms. Phytochromes form a major family of photoreceptors responsible for red light perception in plants, fungi and bacteria. They undergo reversible photoconversion between red-absorbing (Pr) and far-red-absorbing (Pfr) states, thereby ultimately converting a light signal into a distinct biological signal that mediates subsequent cellular responses. Several structures of microbial phytochromes have been determined in their dark-adapted Pr or Pfr states. However, the structural nature of initial photochemical events has not been characterized by crystallography. Here we report the crystal structures of three intermediates in the photoreaction of Pseudomonas aeruginosa bacteriophytochrome (PaBphP). We used cryotrapping crystallography to capture intermediates, and followed structural changes by scanning the temperature at which the photoreaction proceeded. Light-induced conformational changes in PaBphP originate in ring D of the biliverdin (BV) chromophore, and E-to-Z isomerization about the C15 = C16 double bond between rings C and D is the initial photochemical event. As the chromophore relaxes, the twist of the C15 methine bridge about its two dihedral angles is reversed. Structural changes extend further to rings B and A, and to the surrounding protein regions. These data indicate that absorption of a photon by the Pfr state of PaBphP converts a light signal into a structural signal via twisting and untwisting of the methine bridges in the linear tetrapyrrole within the confined protein cavity.

温馨提示:87%用户都在生物谷APP上阅读,扫描立刻下载! 天天精彩!


相关标签

最新会议 培训班 期刊库