l-Amino acid ligase catalyzes dipeptide synthesis from unprotected l-amino acids in an ATP-dependent manner. We have purified a new l-amino acid ligase, RizA, which synthesizes dipeptides whose N-terminus is Arg, from Bacillus subtilis NBRC3134, a microorganism that produces a rhizocticin peptide antibiotic. It was suggested that RizA is probably involved in rhizocticin biosynthesis. In this study, we performed sequence analysis of unknown regions around rizA, and newly identified a gene that encodes a protein that possesses an ATP-grasp motif upstream of rizA. This gene was designated rizB, and its recombinant protein was prepared. Recombinant RizB synthesized homo-oligomers of branched-chain l-amino acids and l-methionine consisting of two to five amino acids in an ATP-dependent manner. RizB also synthesized various heteropeptides. Further examination showed that RizB might elongate a peptide chain at the N-terminus. This is the first report on an l-amino acid ligase catalyzing oligopeptide synthesis.
l-
氨基酸连接酶以一种
ATP 依赖性方式催化未受保护的 l-
氨基酸合成二肽。我们从生产根肿灵
多肽抗生素的
枯草芽孢杆菌 NBRC3134 中纯化出一种新的 l-
氨基酸连接酶 RizA,它能合成 N 端为 Arg 的二肽。有研究认为,RizA 可能参与了
根皮素的
生物合成。在本研究中,我们对 rizA 周围的未知区域进行了序列分析,新发现了一个编码具有
ATP 抓取基序的蛋白质的
基因,该
基因位于 rizA 的上游。该
基因被命名为 rizB,并制备了其
重组蛋白。
重组 RizB 以
ATP 依赖性方式合成由 2 至 5 个
氨基酸组成的支链 l-
氨基酸和 l-蛋
氨酸的同源异构体。RizB 还能合成各种杂肽。进一步研究表明,RizB 可能会在 N 端延长肽链。这是首次报道一种催化寡肽合成的 l-
氨基酸连接酶。