Effects of dilute HCl on yeast tRNA* and E. coli tRNA

HCl treatment of yeast tRNA^h under conditions generally used for excision of 'Y' base results in structure and conformation changes as monitored by line widths in the PMR spectra at 220 MHz and by optical rotation. Like exposure of li.coli tRNAj e t causes similar changes in the PMR spectra and optical rotation although no residues are eliminated. Electrophoresis in polyacrylamide gels provides evidence for aggregation in HCl-treated tRNAj e t . One must thus consider a general effect of HCl exposure as well as possible residue removal in assessing induced structural and conformation changes in tRNA. INTRODUCTION Exposure of yeast tRNA h e to dilute HCl, (Thiebe and Zachau 1968, 1970), results in excision of a fluorescent, highly substituted guanine base, the structure having recently been elucidated (Nakanishi ejt al_, 1970) . The product, tRNA^cf, has been found, by a variety of spectral techniques, to have altered conformational properties (Thiebe and Zachau, 1970). Evidence for perturbed conformation of the anticodon loop has been obtained from studies of complimentary oligonucleotide binding to tRMA^f (Pongs and Reinwald, 1973). Additionally, tRNA^ e displays altered codon response (Thiebe and Zachau, 1970; Ghosh and Ghosh, 1972), as well as somewhat different amino acid charging behavior (Thiebe and Zachau, 1970). Abbreviations: NMR, nuclear magnetic resonance; pmr, proton magnetic resonance.