Conformational differences between the Pfr and Pr states in Pseudomonas aeruginosa bacteriophytochrome
Conformational differences between the Pfr and Pr states in Pseudomonas aeruginosa bacteriophytochrome
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DOI：
10.1073/pnas.0902178106
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发表时间：
2009-09
期刊：
影响因子：
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通讯作者：
Xiaojing Yang;J. Kuk;K. Moffat
中科院分区：
文献类型：
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作者：
Xiaojing Yang;J. Kuk;K. Moffat
光敏色素是红光光受体，其通过在红光（Pr）和远红光（Pfr）光吸收状态之间的可逆光转换来调节植物、真菌和细菌中的光响应。在这里，我们报告的晶体结构的Q188 L突变体的铜绿假单胞菌细菌光敏色素（PaBphP）的光敏核心模块，它具有改变的光转换行为和不同的晶体包装从野生型。我们观察到两个不同的发色团构象的Q188 L晶体结构，我们确定与PFR和Pr状态。Pr/Pfr组合物，不同的晶体，似乎与Q188 L晶体的低温保护的光条件下。我们还比较了所有已知的Pr和Pfr结构。使用定点诱变，我们确定参与稳定胆绿素发色团的15 Ea（Pfr）和15 Za（Pr）构型的残基。具体而言，Ser-261似乎是必不可少的，以形成一个稳定的Pr状态在PaBphP，可能是通过其与环C的丙酸基团的相互作用。我们提出了一个“翻转和旋转”的模型，总结了主要的构象差异之间的Pr和PFR状态的发色团和它的结合口袋。
Phytochromes are red-light photoreceptors that regulate light responses in plants, fungi, and bacteria by means of reversible photoconversion between red (Pr) and far-red (Pfr) light-absorbing states. Here, we report the crystal structure of the Q188L mutant of Pseudomonas aeruginosa bacteriophytochrome (PaBphP) photosensory core module, which exhibits altered photoconversion behavior and different crystal packing from wild type. We observe two distinct chromophore conformations in the Q188L crystal structure that we identify with the Pfr and Pr states. The Pr/Pfr compositions, varying from crystal to crystal, seem to correlate with light conditions under which the Q188L crystals are cryoprotected. We also compare all known Pr and Pfr structures. Using site-directed mutagenesis, we identify residues that are involved in stabilizing the 15Ea (Pfr) and 15Za (Pr) configurations of the biliverdin chromophore. Specifically, Ser-261 appears to be essential to form a stable Pr state in PaBphP, possibly by means of its interaction with the propionate group of ring C. We propose a “flip-and-rotate” model that summarizes the major conformational differences between the Pr and Pfr states of the chromophore and its binding pocket.