科研动态

近日,大发老虎机手机赵开弘课题组与美国伊利诺伊大学芝加哥分校杨晓静和任重博士合作,发现了蓝细菌光受体“橙色胡萝卜素蛋白”实施光合作用光保护的原初分子机制,论文"Photoactivationmechanism of a carotenoid-based photoreceptor"于5月30日在线发表在美国科学院院刊(PNAS)上。

该文章从动态晶体学角度通过时间分辨技术与生物技术等方法对橙色胡萝卜素蛋白的光合作用光保护进行了深入研究。我校赵开弘教授为论文并列通讯作者,博士研究生鲁璐为第三作者。

蓝细菌是最早的光合放氧生物,对地球表面从无氧大气环境变为有氧大气环境发挥了巨大作用。在适当强度的光照条件下,蓝细菌能通过光合作用将光能转换成化学能,生成有机化合物和分子氧以供生命所需,而过强的光照则会对蓝细菌造成严重的损伤。为了应对高光胁迫,蓝细菌进化出了一系列的光合作用光保护机制,而橙色胡萝卜素蛋白是蓝细菌光合作用光保护的关键元件。

蓝细菌光合作用课题组长期研究蓝细菌光合作用,致力于将蓝细菌光合作用高效元件转入植物以提高光合作用生产力,该科研成果为进一步研究蓝细菌高效光合作用机制并为构建全波段光合作用又迈进了一步。

Abstract

Photoprotection is essential for efficient photosynthesis. Cyanobacteria have evolved a unique photoprotective mechanism mediatedby a water-soluble carotenoid-based photoreceptor known as orange carotenoid protein (OCP). OCP undergoes large conformational changes in response to intense blue light, and the photoactivated OCP facilitates dissipation ofexcess energy via direct interaction with allophycocyanins at the phycobilisome core. However, the structural events leading up to the OCP photoactivation remain elusive at the molecular level. Here we present direct observationsof light-induced structural changes in OCP captured by dynamic crystallography. Difference electron densities between the dark and illuminated states reveal widespread and concerted atomic motions that lead to altered protein–pigmentinteractions, displacement of secondary structures, and domain separation. Based on these crystallographic observations together with site-directed mutagenesis, we propose a molecular mechanism for OCP light perception, inwhich the photochemical property of a conjugated carbonyl group is exploited. We hypothesize that the OCP photoactivation starts with keto–enol tautomerization of the essential 4-keto group in the carotenoid, which disruptsthe strong hydrogen bonds between the bent chromophore and the protein moiety. Subsequent structural changes trapped in the crystal lattice offer a high-resolution glimpse of the initial molecular events as OCP begins to transitionfrom the orange-absorbing state to the active red-absorbing state.