Origin, phylogeny, evolution and structural basis of light-driven protochlorophyllide reduction

原叶绿素的还原是产生(细菌)叶绿素的复杂生物合成途径的关键步骤之一。在植物、藻类和蓝藻等富氧光养生物中，这一步骤是由光驱动的原叶绿素(Pchlide)氧化还原酶(LPORs)催化的。在进化的背景下，目前被广泛接受的是LPOR最初是在蓝藻中发明的，然后通过内生共生转移到植物和藻类中。与这一长期存在的共生现象形成对比的是，我们最近在厌氧性α-蛋白细菌Dinorosebacter Shibae DFL12T中发现了一个具有功能的光驱动LPOR(未发表的数据，见前期工作)。这对叶绿素生物合成和光合作用的进化提出了深远的问题，并表明在不可培养的菌株和/或专门的微生物中可能发现额外的功能多样化的LPOR。该提案旨在利用尚未探索的元基因组/环境来源的序列多样性来阐明光驱动原叶绿素还原的进化起源、系统发育以及结构和功能基础。为了实现这些目标，需要结合微生物学家、分子生物学家、生物化学家、生物信息学家和结构生物学家的跨学科专业知识。虽然体内和体外的功能和结构数据(工作组Krauss和Depper)将提供对LPOR家族光驱Pchlide还原的功能适应和机制方面的广泛见解，但Arndt von Haeseler工作组将建立的进化视角有望提供新的维度和丰富的范围。

The reduction of protochlorophyllide represents one key steps in the complex biosynthesis pathway yielding (bacterio)chlorophyll. In oxygenic phototrophs such as plants, algae and cyanobacteria this step is catalyzed by light-driven protochlorophyllide (Pchlide) oxidoreductases (LPORs). In an evolutionary context, it is currently widely accepted that LPORs were first -invented- in cyanobacteria and were then transferred via endosymbiosis to plants and algae. In contrast to this long held paragdigm, we have recently identified a functional light-driven LPOR in the anoxygenic alpha-proteobacterium Dinoroseobacter shibae DFL12T (unpublished data, see preliminary work). This raises far reaching questions regarding the evolution of chlorophyll biosynthesis and photosynthesis and suggests that additional functionally diverse LPORs might be found in e.g. unculturable strains and/or specialized microbes. The proposal aims to exploit the yet unexplored sequence diversity of metagenomic/environmental sources to elucidate the evolutionary origin, phylogeny, as well as the structural and functional basis of light-driven protochlorophyllide reduction. To achieve these goals, it is necessary to combine the interdisciplinary expertise of microbiologists, molecular biologists, biochemists, bioinformaticians and structural biologists. While in vivo and in vitro functional and structural data (working groups Krauss and Drepper) will provide broad insight into functional adaptation and mechanistic aspects of light-driven Pchlide reduction by the LPOR family of enzymes, the evolutionary perspective which will be established by the working group of Arndt von Haeseler is expected to provide a new dimension and enriched scope.