Mutational analysis of conserved nucleotides in a self-splicing group I intron

Sandra Couture, Andrew D. Ellington, Anne S. Gerber, J. Michael Cherry, Jennifer A. Doudna, Rachel Green, Maya Hanna, Umberto Pace, Jayaraj Rajagopal, Jack W. Szostak

Research output: Contribution to journalArticlepeer-review

69 Scopus citations


We have constructed all single base substitutions in almost all of the highly conserved residues of the Tetrahymena self-splicing intron. Mutation of highly conserved residues almost invariably bleads to loss of enzymatic activity. In many cases, activity could be regained by making additional mutations that restored predicted base-pairings; these second site suppressors in general confirm the secondary structure derived from phylogenetic data. At several positions, our suppression data can be most readily explained by assuming non-Watson-Crick base-pairings. In addition to the requirements imposed by the secondary structure, the sequence of the intron is constrained by “negative interactions”, the exclusion of particular nucleotide sequences that would form undersirable secondary structures. A comparison of genetic and phylogenetic data suggests sites that may be involved in tertiary structural interactions.

Original languageEnglish (US)
Pages (from-to)345-358
Number of pages14
JournalJournal of molecular biology
Issue number3
StatePublished - 1990
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Biology
  • Biophysics
  • Structural Biology


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