title: Catalytically critical nucleotide in domain 5 of a group II intron.
abstract: Domain 5 (D5) is a small hairpin structure within group II introns. A bimolecular assay system depends on binding by D5 to an intron substrate for self-splicing activity. In this study, mutations in D5 identify two among six nearly invariant nucleotides as being critical for 5' splice junction hydrolysis but unimportant for binding. A mutation at another site in D5 blocks binding. Thus, mutations can distinguish two D5 functions: substrate binding and catalysis. The secondary structure of D5 may resemble helix I formed by the U2 and U6 small nuclear RNAs in the eukaryotic spliceosome. Our results support a revision of the previously proposed correspondence between D5 and helix I on the basis of the critical trinucleotide 5'-AGC-3' present in both. We suggest that this trinucleotide plays a similar role in promoting the chemical reactions for both splicing systems.
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, PA 15260-7700, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Peebles
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: P S
authors.initials: PS
authors.lastname: Perlman
authors.forename: J S
authors.initials: JS
authors.lastname: Franzen
mesh_terms: D001482:Base Composition; D001483:Base Sequence; D001667:Binding, Competitive; D002384:Catalysis; D017124:Conserved Sequence; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D014644:Genetic Variation; D007438:Introns; D007700:Kinetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D012322:RNA Precursors / Q000737:chemistry / Q000378:metabolism; D012326:RNA Splicing; D012044:Regression Analysis; D013698:Templates, Genetic; D013816:Thermodynamics; D014158:Transcription, Genetic; D014764:Viral Proteins
chemical_list: D012322:RNA Precursors; D014764:Viral Proteins; D012313:RNA; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases