title: RNA ligase structures reveal the basis for RNA specificity and conformational changes that drive ligation forward.
abstract: T4 RNA ligase 2 (Rnl2) and kinetoplastid RNA editing ligases exemplify a family of RNA repair enzymes that seal 3'OH/5'PO(4) nicks in duplex RNAs via ligase adenylylation (step 1), AMP transfer to the nick 5'PO(4) (step 2), and attack by the nick 3'OH on the 5'-adenylylated strand to form a phosphodiester (step 3). Crystal structures are reported for Rnl2 at discrete steps along this pathway: the covalent Rnl2-AMP intermediate; Rnl2 bound to an adenylylated nicked duplex, captured immediately following step 2; and Rnl2 at an adenylylated nick in a state poised for step 3. These structures illuminate the stereochemistry of nucleotidyl transfer and reveal how remodeling of active-site contacts and conformational changes propel the ligation reaction forward. Mutational analysis and comparison of nick-bound structures of Rnl2 and human DNA ligase I highlight common and divergent themes of substrate recognition that can explain their specialization for RNA versus DNA repair.
authors.affiliation: Structural Biology Program, Sloan-Kettering Institute, New York, NY 10021, USA.
authors.forename: Jayakrishnan
authors.initials: J
authors.lastname: Nandakumar
authors.forename: Stewart
authors.initials: S
authors.lastname: Shuman
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Lima
mesh_terms: D000249:Adenosine Monophosphate / Q000737:chemistry / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000737:chemistry; D004252:DNA Mutational Analysis; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D011130:RNA Ligase (ATP) / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: C000607892:LIG1 protein, human; D014764:Viral Proteins; D000249:Adenosine Monophosphate; D012313:RNA; D000255:Adenosine Triphosphate; D011088:DNA Ligases; D000072481:DNA Ligase ATP; D011130:RNA Ligase (ATP); C467724:bacteriophage T4 RNA ligase 2