小柯机器人

叶绿素生物合成中酶促光催化的结构基础，这一成果由英国曼彻斯特大学Nigel S. Scrutton、中国农业科学院程奇和上海交通大学周爱武等研究人员合作取得。2019年10月23日，《自然》杂志在线发表了这项成果。

研究人员报道了从Thermosynechococcus elongatus和Synechocystis sp的原叶绿素酸酯氧化还原酶（POR）晶体结构，包括游离形式和与烟酰胺辅酶复合的形成。研究人员的原叶绿素酸酯–NADPH–POR三元复合物结构模型和模拟确定了POR活性位点中的多种相互作用，这对于原叶绿素酸酯的结合、光敏化和光化学转化为叶绿素很重要。

研究人员证明了使用POR变体和原叶绿素类似物进行实验时，活性位点结构和原叶绿素结构在驱动POR光化学中的重要性。这些研究揭示了，POR活性位点如何通过从NADPH进行的局部氢化物转移和沿结构定义的质子转移途径的远距离质子转移，来促进光驱动的原叶绿素酸酯减少。

据了解，POR催化叶绿素生物合成中的光依赖性步骤，这对光合作用至关重要，并且最终对地球上的所有生命至关重要。POR是三种已知的光依赖性酶之一，它催化光敏剂和底物原叶绿素的还原，形成色素叶绿素。尽管其生物学重要性，POR光催化的结构基础仍然未知。

附：英文原文

Title: Structural basis for enzymatic photocatalysis in chlorophyll biosynthesis

Author: Shaowei Zhang, Derren J. Heyes, Lingling Feng, Wenli Sun, Linus O. Johannissen, Huanting Liu, Colin W. Levy, Xuemei Li, Ji Yang, Xiaolan Yu, Min Lin, Samantha J. O. Hardman, Robin Hoeven, Michiyo Sakuma, Sam Hay, David Leys, Zihe Rao, Aiwu Zhou, Qi Cheng, Nigel S. Scrutton

Issue&Volume: 2019-10-23

Abstract: The enzyme protochlorophyllide oxidoreductase (POR) catalyses a light-dependent step in chlorophyll biosynthesis that is essential to photosynthesis and, ultimately, all life on Earth1,2,3. POR, which is one of three known light-dependent enzymes4,5, catalyses reduction of the photosensitizer and substrate protochlorophyllide to form the pigment chlorophyllide. Despite its biological importance, the structural basis for POR photocatalysis has remained unknown. Here we report crystal structures of cyanobacterial PORs from Thermosynechococcus elongatus and Synechocystis sp. in their free forms, and in complex with the nicotinamide coenzyme. Our structural models and simulations of the ternary protochlorophyllide–NADPH–POR complex identify multiple interactions in the POR active site that are important for protochlorophyllide binding, photosensitization and photochemical conversion to chlorophyllide. We demonstrate the importance of active-site architecture and protochlorophyllide structure in driving POR photochemistry in experiments using POR variants and protochlorophyllide analogues. These studies reveal how the POR active site facilitates light-driven reduction of protochlorophyllide by localized hydride transfer from NADPH and long-range proton transfer along structurally defined proton-transfer pathways.

DOI: 10.1038/s41586-019-1685-2

Source: https://www.nature.com/articles/s41586-019-1685-2

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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