A chemical approach to studies of the three-dimensional structure of tRNA - alkylation with a reagent covalently bound to a "peculiar site'.

Yeast valine tRNA1 was chemically modified with chlorambucil N-hydroxysuccinimide ester. tthe reagent was attached covalently to the valine residue of valyl-tRNA1Val under the conditions which prevented tRNA from alkylation. Chlorambucilyl-valyl-tRNA1Val thus obtained was separated from excess reagent and incubated in an aqueous solution at neutral pH in the presence of Mg++ions. Highly efficient intramolecular self-alkylation of chlorambucilyl-valyl-tRNA1Val took place. The chlorambucil residue bound covalently to the amino group of the valine residue of tRNA1Val alkylates the 5'-terminal phosphate group of the molecule, and its 3'-terminal sequence -A-C-C-A.