Inactivation of Valine Acceptor Activity by a C→U Missense Change in the Anticodon of Yeast Valine Transfer Ribonucleic Acid

Abstract

Abstract Six C→U transitions have been produced in yeast tRNA1val with 3.2 m NaHSO3 at pH 5.8 and 25°. The reactive residues are located at C17 (dihydrouridine loop); C37 (anticodon); C39 (anticodon loop); C72, C74, and C75 (near the 3' terminus). Of these 6 residues 2 are inactivation targets and 1 is located in the anticodon (C37). The position of the 2nd is still uncertain, but it is located near the 3' terminus at either C72 or C75. C→U transitions in either of these targets destroy the valine acceptor activity, measured under standard, in vitro assay conditions. The data demonstrate unambiguously that a C→U missense change (Val→Ile) occurring in the third position of the anticodon of yeast tRNA1val destroys its normal acceptor activity.