Nishida Hiromi, Ohnishi Yasuo, Beppu Teruhiko, Horinouchi Sueharu
Agricultural Bioinformatics Research Unit, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
Environ Microbiol. 2007 Aug;9(8):1986-94. doi: 10.1111/j.1462-2920.2007.01314.x.
The gamma-butyrolactone regulatory system triggers secondary metabolism and/or morphological development in the Gram-positive, soil-dwelling, filamentous bacterial genus Streptomyces. The representative of the gamma-butyrolactones is A-factor in Streptomyces griseus. AfsA is an enzyme for A-factor biosynthesis and ArpA is the A-factor receptor protein that serves as a transcriptional factor by using A-factor as the ligand. Analysis of evolutional relations between AfsA including its homologues and ArpA including its homologues, all of which are widely distributed in Streptomyces, revealed great differences in the topologies of their phylogenetic trees. Therefore, the combinations of AfsA homologues and ArpA homologues in a given Streptomyces strain appear to have changed during the evolution. Even if an afsA homologue and an arpA homologue locate adjacently on the chromosome, the evolutional history of the individuals was found to be different in some Streptomyces strains. In addition, the phylogenetic analyses suggested that the ancestral ArpA protein had existed and functioned as a DNA-binding protein, not as a gamma-butyrolactone receptor, before the appearance of a gamma-butyrolactone receptor protein in the course of the bacterial evolution. Some Streptomyces strains have plasmids encoding AfsA/ArpA homologues, which suggests that plasmids have played an important role in the distribution of afsA/arpA homologues. During the evolution, once a Streptomyces strain acquired different afsA/arpA homologues, it may have developed a new gamma-butyrolactone regulatory system reconstructing the regulatory systems for secondary metabolism and/or morphogenesis. This idea is consistent with the diverged combination of AfsA homologues and ArpA homologues in a Streptomyces strain.
γ-丁内酯调控系统可触发革兰氏阳性、土壤栖息、丝状细菌属链霉菌的次生代谢和/或形态发育。γ-丁内酯的代表物是灰色链霉菌中的A因子。AfsA是一种参与A因子生物合成的酶，而ArpA是A因子受体蛋白，它以A因子作为配体，作为转录因子发挥作用。对包括其同源物在内的AfsA和包括其同源物在内的ArpA之间的进化关系进行分析，发现它们在链霉菌中广泛分布，其系统发育树的拓扑结构存在很大差异。因此，在给定的链霉菌菌株中，AfsA同源物和ArpA同源物的组合在进化过程中似乎发生了变化。即使一个afsA同源物和一个arpA同源物在染色体上相邻定位，在一些链霉菌菌株中也发现个体的进化历史是不同的。此外，系统发育分析表明，在细菌进化过程中γ-丁内酯受体蛋白出现之前，祖先的ArpA蛋白就已存在并作为一种DNA结合蛋白发挥作用，而不是作为γ-丁内酯受体。一些链霉菌菌株含有编码AfsA/ArpA同源物的质粒，这表明质粒在afsA/arpA同源物的分布中发挥了重要作用。在进化过程中，一旦链霉菌菌株获得了不同的afsA/arpA同源物，它可能就会发展出一种新的γ-丁内酯调控系统，从而重建次生代谢和/或形态发生的调控系统。这一观点与链霉菌菌株中AfsA同源物和ArpA同源物的不同组合是一致的。
