Riera J, Robb F T, Weiss R, Fontecave M
Laboratoire d'Etudes Dynamiques et Structurales de la Sélectivité, Unité Mixte de Recherches Centre National de la Recherche Scientifique 5616, Université, Joseph Fourier, Grenoble, France.
Proc Natl Acad Sci U S A. 1997 Jan 21;94(2):475-8. doi: 10.1073/pnas.94.2.475.
Ribonucleotide reductase (RNR), the enzyme responsible for deoxyribonucleotide synthesis, has been isolated from Pyrococcus furiosus, a deeply branching hyperthermophilic, strictly anaerobic archaeon. Its gene has been cloned, sequenced, and shown to harbor two insertions encoding inteins. The purified enzyme absolutely requires adenosylcobalamin for activity, a trait that defines it as a member of class II (adenosyl-cobalamin-dependent) prokaryotic RNRs. On the other hand, the archaeal RNR has significant amino acid sequence homology with class I (aerobic non-heme iron-dependent) and class III (anaerobic iron-sulfur-dependent) RNRs present in eukaryotes and bacteria, respectively. It is proposed that this enzyme may be the closest possible relative of the original RNR, which allowed the key "RNA world" to "DNA world" transition, and that the different classes of present-day RNRs are the products of divergent evolution.
核糖核苷酸还原酶(RNR)是负责脱氧核糖核苷酸合成的酶,已从嗜热栖热菌(一种深度分支的嗜热、严格厌氧古菌)中分离出来。其基因已被克隆、测序,并显示含有两个编码内含肽的插入序列。纯化后的酶的活性绝对需要腺苷钴胺素,这一特性将其定义为II类(依赖腺苷钴胺素)原核RNR的成员。另一方面,古菌RNR与真核生物和细菌中分别存在的I类(好氧非血红素铁依赖性)和III类(厌氧铁硫依赖性)RNR具有显著的氨基酸序列同源性。有人提出,这种酶可能是原始RNR最接近的亲属,它促成了关键的“RNA世界”到“DNA世界”的转变,而当今不同类别的RNR是趋异进化的产物。