Institute of Food Research, Norwich Research Park, Colney, Norwich NR47UA, UK.
Mol Microbiol. 2011 Aug;81(4):1109-24. doi: 10.1111/j.1365-2958.2011.07757.x. Epub 2011 Jul 18.
We have identified gene fusions of polyamine biosynthetic enzymes S-adenosylmethionine decarboxylase (AdoMetDC, speD) and aminopropyltransferase (speE) orthologues in diverse bacterial phyla. Both domains are functionally active and we demonstrate the novel de novo synthesis of the triamine spermidine from the diamine putrescine by fusion enzymes from β-proteobacterium Delftia acidovorans and δ-proteobacterium Syntrophus aciditrophicus, in a ΔspeDE gene deletion strain of Salmonella enterica sv. Typhimurium. Fusion proteins from marine α-proteobacterium Candidatus Pelagibacter ubique, actinobacterium Nocardia farcinica, chlorobi species Chloroherpeton thalassium, and β-proteobacterium D. acidovorans each produce a different profile of non-native polyamines including sym-norspermidine when expressed in Escherichia coli. The different aminopropyltransferase activities together with phylogenetic analysis confirm independent evolutionary origins for some fusions. Comparative genomic analysis strongly indicates that gene fusions arose by merger of adjacent open reading frames. Independent fusion events, and horizontal and vertical gene transfer contributed to the scattered phyletic distribution of the gene fusions. Surprisingly, expression of fusion genes in E. coli and S. Typhimurium revealed novel latent spermidine catabolic activity producing non-native 1,3-diaminopropane in these species. We have also identified fusions of polyamine biosynthetic enzymes agmatine deiminase and N-carbamoylputrescine amidohydrolase in archaea, and of S-adenosylmethionine decarboxylase and ornithine decarboxylase in the single-celled green alga Micromonas.
我们已经在不同的细菌门中鉴定了多胺生物合成酶 S-腺苷甲硫氨酸脱羧酶（AdoMetDC，speD）和氨基丙基转移酶（speE）同源物的基因融合。这两个结构域都具有功能活性，我们通过β变形菌 Delftia acidovorans 和δ变形菌 Syntrophus aciditrophicus 的融合酶证明了新型从头合成三胺亚精胺，该融合酶来自沙门氏菌 sv Typhimurium 的ΔspeDE 基因缺失株。海洋α变形菌 Candidatus Pelagibacter ubique、放线菌 Nocardia farcinica、绿菌门物种 Chloroherpeton thalassium 和β变形菌 D. acidovorans 的融合蛋白在大肠杆菌中表达时，各自产生不同的非天然多胺谱，包括对称-norspermidine。不同的氨基丙基转移酶活性以及系统发育分析证实了一些融合的独立进化起源。比较基因组分析强烈表明，基因融合是通过相邻开放阅读框的合并而产生的。独立的融合事件以及水平和垂直基因转移导致了基因融合在系统发育上的分散分布。令人惊讶的是，融合基因在大肠杆菌和沙门氏菌中的表达揭示了这些物种中新型潜在的亚精胺分解代谢活性，产生非天然的 1,3-二氨基丙烷。我们还在古菌中鉴定了多胺生物合成酶胍氨酸脱氨酶和 N-碳酰胺腐胺酰胺水解酶的融合，以及单细胞绿藻 Micromonas 中的 S-腺苷甲硫氨酸脱羧酶和鸟氨酸脱羧酶的融合。
