期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2002
卷号：99
期号：20
页码：12709-12714
DOI：10.1073/pnas.192184699
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：RNA ligases participate in repair, splicing, and editing pathways that either reseal broken RNAs or alter their primary structure. Bacteriophage T4 RNA ligase (gp63) is the best-studied member of this class of enzymes, which includes yeast tRNA ligase and trypanosome RNA-editing ligases. Here, we identified another RNA ligase from the bacterial domain--a second RNA ligase (Rnl2) encoded by phage T4. Purified Rnl2 (gp24.1) catalyzes intramolecular and intermolecular RNA strand joining through ligase-adenylate and RNA-adenylate intermediates. Mutational analysis identifies amino acids required for the ligase-adenylation or phosphodiester synthesis steps of the ligation reaction. The catalytic residues of Rnl2 are located within nucleotidyl transferase motifs I, IV, and V that are conserved in DNA ligases and RNA capping enzymes. Rnl2 has scant amino acid similarity to T4 gp63. Rather, Rnl2 exemplifies a distinct ligase family, defined by variant motifs, that includes the trypanosome-editing ligases and a group of putative RNA ligases encoded by eukaryotic viruses (baculoviruses and an entomopoxvirus) and many species of archaea. These findings have implications for the evolution of covalent nucleotidyl transferases and virus-host dynamics based on RNA restriction and repair.
