title: Archaeal RNA ligase is a homodimeric protein that catalyzes intramolecular ligation of single-stranded RNA and DNA.
abstract: RNA ligases participate in repair, splicing and editing pathways that either reseal broken RNAs or alter their primary structure. Here, we report the characterization of an RNA ligase from the thermophilic archaeon, Methanobacterium thermoautotrophicum. The 381-amino acid Methanobacterium RNA ligase (MthRnl) catalyzes intramolecular ligation of 5'-PO(4) single-strand RNA to form a covalently closed circular RNA molecule through ligase-adenylylate and RNA-adenylylate (AppRNA) intermediates. At the optimal temperature of 65 degrees C, AppRNA was predominantly ligated to a circular product. In contrast, at 35 degrees C, phosphodiester bond formation was suppressed and the majority of the AppRNA was deadenylylated. Sedimentation analysis indicates that MthRnl is a homodimer in solution. The C-terminal 127-amino acid segment is required for dimerization, is itself capable of oligomeization and acts in trans to inhibit the ligation activity of native MthRnl. MthRnl can also join single-stranded DNA to form a circular molecule. The lack of specificity for RNA and DNA by MthRnl may exemplify an undifferentiated ancestral stage in the evolution of ATP-dependent ligases.
authors.affiliation: Department of Biological Sciences and Department of Microbiology and Immunology, State University of New York at Buffalo, Buffalo, NY 14260, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Torchia
authors.forename: Yuko
authors.initials: Y
authors.lastname: Takagi
authors.forename: C Kiong
authors.initials: CK
authors.lastname: Ho
mesh_terms: D019843:Archaeal Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002384:Catalysis; D004277:DNA, Single-Stranded / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D017014:Methanobacterium / Q000201:enzymology*; D009713:Nucleotidyltransferases / Q000302:isolation & purification / Q000378:metabolism; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D011130:RNA Ligase (ATP) / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017384:Sequence Deletion
chemical_list: D019843:Archaeal Proteins; D004277:DNA, Single-Stranded; D012313:RNA; D009713:Nucleotidyltransferases; C020658:glutamine-synthetase adenylyltransferase; D011130:RNA Ligase (ATP)