Influence of the A15 mutation on the conformational energy balance in Escherichia coli tRNATyr

V. Leon, S. Altman, D. M. Crothers

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3 Scopus citations


The A15 mutation in Escherichia coli tRNAsu3Tyr produces a transfer RNA whose tertiary structure has either a higher or lower tm than the wild type, depending on Mg2+ concentration. The enthalpy that stabilizes the tertiary structure is greatly reduced by the A15 mutation, but there are large compensating entropy changes. At 37 °C the mutation decreases the magnitude of the free energy stabilizing the tertiary structure for all Mg2+ concentrations. The nucleotide modifications s4U, iA and G* do not contribute detectably to tertiary structure stability. The results can be interpreted in terms of a tertiary pairing between A15 and C57 in tRNAsu3 A15Tyr, of a form suggested by the unusual bonding between G15 and C48 found in crystallographic studies of yeast tRNAphe. The observed disturbance in the conformational energy balance should contribute to the defective function of tRNAsu3 A15Tyr.

Original languageEnglish (US)
Pages (from-to)253-265
Number of pages13
JournalJournal of molecular biology
Issue number1
StatePublished - Jun 15 1977
Externally publishedYes

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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