Abstract
In the reaction of yeast alanine transfer RNA with nitrous acid, interior nucleotides deaminate relatively slowly with the order of reactivity CMP > AMP ≅ GMP instead of GMP > AMP > CMP, the order found for mononucleotides. Approximately 20% of the cytidylic acid residues in yeast tRNAAla are deaminated before there is detectable reaction of guanylic acid or interior adenylic acid residues. The 3′-terminal adenylic acid residue is reactive, and this reaction leads to the loss of alanine acceptor activity. If the terminal adenylic residue is missing from the RNA, deamination of the 3′-terminal cytidylic acid leads to loss of acceptor activity for adenylic acid, as well as alanine. Interior deamination at certain positions leads to loss of alanine acceptor activity, but yeast tRNAAla deaminated in the anticodon or in the “dihydrouracil loop” is still active. Deamination in the anticodon, which changes the IGC sequence to IGU, alters the specificity of the transfer reaction of tRNAAla to that expected for tRNAThr.
Published Version
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