title: Crystal structure of the catalytic core of an RNA-polymerase ribozyme.
abstract: Primordial organisms of the putative RNA world would have required polymerase ribozymes able to replicate RNA. Known ribozymes with polymerase activity best approximating that needed for RNA replication contain at their catalytic core the class I RNA ligase, an artificial ribozyme with a catalytic rate among the fastest of known ribozymes. Here we present the 3.0 angstrom crystal structure of this ligase. The architecture resembles a tripod, its three legs converging near the ligation junction. Interacting with this tripod scaffold through a series of 10 minor-groove interactions (including two A-minor triads) is the unpaired segment that contributes to and organizes the active site. A cytosine nucleobase and two backbone phosphates abut the ligation junction; their location suggests a model for catalysis resembling that of proteinaceous polymerases.
authors: Whitehead Institute for Biomedical Research and Howard Hughes Medical Institute, 9 Cambridge Center, Cambridge, MA 02142, USA.
authors: David M
authors: DM
authors: Shechner
authors: Robert A
authors: RA
authors: Grant
authors: Sarah C
authors: SC
authors: Bagby
authors: Yelena
authors: Y
authors: Koldobskaya
authors: Joseph A
authors: JA
authors: Piccirilli
authors: David P
authors: DP
authors: Bartel
mesh_terms: D020029:Base Pairing; D001483:Base Sequence; D002384:Catalysis; D020134:Catalytic Domain; D003460:Crystallization; D018360:Crystallography, X-Ray; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000378:metabolism; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011118:Polynucleotide Ligases / Q000737:chemistry / Q000378:metabolism; D016337:RNA, Catalytic / Q000737:chemistry* / Q000378:metabolism; D012265:Ribonucleotides / Q000737:chemistry / Q000378:metabolism
chemical_list: D016337:RNA, Catalytic; D012265:Ribonucleotides; D012321:DNA-Directed RNA Polymerases; D011118:Polynucleotide Ligases; D008274:Magnesium