Regulation of Tetrapyrrole Synthesis in Rhodobacter capsulatus

光合细菌利用一条分支途径 合成所有四种四吡咯终产物：血红素， 细菌叶绿素、维生素B-12和西罗血红素。 什么让 这条分支途径非常有趣， 产品在细胞代谢中起着如此不同的作用， 所需的量有很大的不同 最终目标 这项研究的目的是了解植物的光合作用 荚膜红细菌协调合成 四个四吡咯产物。 最近的证据表明 PufQ蛋白与四吡咯中间体结合 并参与其转化为细菌叶绿素。 因此，细菌叶绿素的合成受 存在于细胞中的PufQ蛋白的量。 的作用 载体蛋白如PufQ在调节常见的 四吡咯途径，导致血红素和 正在测定细菌叶绿素。 当粪卟啉 从R. capsulatus它与一个32kDa的 蛋白质太大，不能成为PufQ。 这种蛋白质被 部分测序，使用寡核苷酸克隆基因 探针，以及构建的缺乏该蛋白质的突变体。 的 该突变体的表型允许确定 无论这种蛋白质是血红素合成所必需的， 细菌叶绿素合成，或两者。 其他hem突变体 被分离出来，这样就可以确定 四吡咯中间体首先与载体结合 蛋白 可以说，导致蛋白质合成的生物合成途径 四吡咯如叶绿素和血红素的产生， 自然界中最重要的途径之一。 目前， 关于这个复杂的途径是如何 监管. 光合细菌红细菌 capsulatus提供了一个理想的模型系统，因为它 合成所有四种四吡咯终产物， 来研究基因和生物化学。 本研究 旨在了解一个充分而平衡的 确保了这些化合物的供应。//

Photosynthetic bacteria use a single branched pathway to synthesize all four tetrapyrrole endproducts: heme, bacteriochlorophyll, vitamin B-12, and siroheme. What makes this branched pathway so interesting is that the four products play such diverse roles in cellular metabolism and are required in vastly different amounts. The ultimate aim of this research is to understand how the photosynthetic bacterium Rhodobacter capsulatus coordinates the synthesis of the four tetrapyrrole products. Recent evidence suggests that the PufQ protein binds to some tetrapyrrole intermediate and is involved in its conversion to bacteriochlorophyll. Synthesis of bacteriochlorophyll is therefore regulated by the amount of PufQ protein present in the cell. The role of carrier proteins such as PufQ in the regulation of the common tetrapyrrole pathway that leads to heme and bacteriochlorophyll is being determined. When coproporphyrin is excreted from R. capsulatus it is complexed with a 32kDa protein which is too large to be PufQ. This protein is being partially sequenced, the gene cloned using oligonucleotide probes, and a mutant constructed that lacks the protein. The phenotype of this mutant allows for a determination of whether this protein is required for heme synthesis, bacteriochlorophyll synthesis, or both. Other hem mutants are being isolated so that it can be determined which tetrapyrrole intermediate is the first to bind a carrier protein. It can be argued that the biosynthetic pathway leading to the production of tetrapyrroles such as chlorophyll and heme is one of the most important pathways in nature. Currently, very little is known about how this complex pathway is regulated. The photosynthetic bacterium Rhodobacter capsulatus provides an ideal model system, in that it synthesizes all four tetrapyrrole endproducts and is amenable to study both genetically and biochemically. This research aims at an understanding of how an adequate yet balanced supply of these compounds is ensured. //