Three classes of oxygen-dependent cyclase involved in chlorophyll and bacteriochlorophyll biosynthesis
Three classes of oxygen-dependent cyclase involved in chlorophyll and bacteriochlorophyll biosynthesis
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DOI：
10.1073/pnas.1701687114
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发表时间：
2017-06-13
影响因子：
11.1
通讯作者：
Hunter, C. Neil
中科院分区：
文献类型：
--
作者：
Chen, Guangyu E.;Canniffe, Daniel P.;Hunter, C. Neil
（细菌）叶绿素色素的生物合成是地球上最具生产力的生物途径之一。光合作用依赖于这些修饰的四吡咯来捕获太阳辐射并将其转化为化学能。（细菌）叶绿素有一个同环的第五个环，其形成仍然是谜超过60年。该反应由两种不相关的环化酶使用不同的化学反应催化。大多数的无氧光合细菌使用BchE，O-2-敏感的[4Fe-4S]簇蛋白，而植物，蓝细菌，和一些光合细菌具有O-2依赖性酶，其主要催化成分是二铁蛋白，AcsF。植物和蓝藻突变体ycf 54显示受损的功能的O-2-依赖性酶，积累反应底物。蓝细菌和紫色光养细菌之间的交换环化酶揭示了三类O-2依赖性酶。AcsF来自紫色β-变形杆菌Rubrivivax（Rvi.）gelatinosus不仅挽救了集胞藻属PCC 6803中的蓝藻直系同源物cycI的损失，而且挽救了ycf 54的损失;相反，需要蓝藻cycI和ycf 54的共表达来补充Rvi中acsF的损失。胶状的这些结果表明，Ycf 54是一个环化酶亚基在产氧光养生物，和不同类别的酶存在的基础上，他们需要一个额外的亚基。AcsF是Rvi中的环化酶。gelatinosus，而α-变形菌环化酶需要一种新发现的蛋白质，我们称之为BciE，由这些生物体中保守的基因编码。这些数据描绘了三个类的O-2依赖性环化酶在chlorphotototrophic生物从高等植物细菌，和它们的进化进行了讨论。
The biosynthesis of (bacterio) chlorophyll pigments is among the most productive biological pathways on Earth. Photosynthesis relies on these modified tetrapyrroles for the capture of solar radiation and its conversion to chemical energy. (Bacterio) chlorophylls have an isocyclic fifth ring, the formation of which has remained enigmatic for more than 60 y. This reaction is catalyzed by two unrelated cyclase enzymes using different chemistries. The majority of anoxygenic phototrophic bacteria use BchE, an O-2-sensitive [4Fe-4S] cluster protein, whereas plants, cyanobacteria, and some phototrophic bacteria possess an O-2-dependent enzyme, the major catalytic component of which is a diiron protein, AcsF. Plant and cyanobacterial mutants in ycf54 display impaired function of the O-2-dependent enzyme, accumulating the reaction substrate. Swapping cyclases between cyanobacteria and purple phototrophic bacteria reveals three classes of the O-2-dependent enzyme. AcsF from the purple betaproteobacterium Rubrivivax (Rvi.) gelatinosus rescues the loss not only of its cyanobacterial ortholog, cycI, in Synechocystis sp. PCC 6803, but also of ycf54; conversely, coexpression of cyanobacterial cycI and ycf54 is required to complement the loss of acsF in Rvi. gelatinosus. These results indicate that Ycf54 is a cyclase subunit in oxygenic phototrophs, and that different classes of the enzyme exist based on their requirement for an additional subunit. AcsF is the cyclase in Rvi. gelatinosus, whereas alphaproteobacterial cyclases require a newly discovered protein that we term BciE, encoded by a gene conserved in these organisms. These data delineate three classes of O-2-dependent cyclase in chlorophototrophic organisms from higher plants to bacteria, and their evolution is discussed herein.