光合生物使用两种不同的酶来还原原叶绿素(Pchlide)的C17=C18双键,产生叶绿素前体叶绿素。首先,类似固氮酶的,不依赖光的(黑暗手术)普氏氧化还原酶,其次,光依赖性Pchlide氧化还原酶(LPOR)。对于后一种酶,尽管进行了几十年的研究,没有可用的结构信息。这里,我们使用蛋白质结构建模,分子动力学(MD)模拟与多波长分析超速离心(MWA-AUC)和小角X射线散射(SAXS)实验相结合,得出LPOR载脂蛋白和底物/辅因子/LPOR三元复合物的共识模型。MWA-AUC和SAXS实验独立证明载脂蛋白是单体,而三元络合物的形成诱导二聚化。SAXS指导的建模研究提供了载脂蛋白的全长模型,并提出了LPOR三元复合物二聚化的试探性模式,由已发布的交叉链接约束支持。我们的研究提供了LPOR结构组织的第一印象。
Photosynthetic organisms employ two different enzymes for the reduction of the C17 = C18 double bond of protochlorophyllide (Pchlide), yielding the chlorophyll precursor chlorophyllide. First, a nitrogenase-like, light-independent (dark-operative) Pchlide oxidoreductase and secondly, a light-dependent Pchlide oxidoreductase (LPOR). For the latter enzyme, despite decades of research, no structural information is available. Here, we use protein structure modelling, molecular dynamics (MD) simulations combined with multi-wavelength analytical ultracentrifugation (MWA-AUC) and small angle X-ray scattering (SAXS) experiments to derive a
consensus model of the LPOR apoprotein and the substrate/cofactor/LPOR ternary complex. MWA-AUC and SAXS experiments independently demonstrate that the apoprotein is monomeric, while ternary complex formation induces dimerization. SAXS-guided modelling studies provide a full-length model of the apoprotein and suggest a tentative mode of dimerization for the LPOR ternary complex, supported by published cross-link constraints. Our study provides a first impression of the LPOR structural organization.