The Yeast Phenylalanyl-Transfer RNA Synthetase Recognition Site: The Region Adjacent to the Dihydrouridine Loop

¹Department of Biochemistry, State University of New York at Stony Brook, Stony Brook, N. Y. 11790

Abstract

Purified yeast phenylalanyl-tRNA synthetase can aminoacylate (yeast) tRNA^Phe, (wheat) tRNA^Phe, and (Escherichia coli) tRNA₁ ^Val (1, 2). We now report that this synthetase can also aminoacylate (E. coli) tRNA^Phe and (E. coli) tRNA₁ ^Ala. Highly purified (E. coli) tRNA^Phe is heterologously aminoacylated to approximately 90% of the extent achieved with the homologous enzyme (crude E. coli phenylalanyl-tRNA synthetase). Pure (E. coli) tRNA₁ ^Ala (the major species) is heterologously aminoacylated to 70% of the extent achieved with the homologous synthetase (crude E. coli alanyl-tRNA synthetase).

(E. coli) tRNA^Phe is the fourth purified transfer RNA of known sequence to be shown to be an acceptable substrate for purified yeast phenylalanyl-tRNA synthetase. A comparison of these sequences shows that only one region is extremely similar in all four tRNAs. This region is located adjacent to the dihydrouridine loop, and consists of the nucleotides [Formula: see text] We conclude that this is the synthetase recognition site for yeast phenylalanyl-tRNA synthetase.

This conclusion is further supported by partial fragment analysis of (E. coli) tRNA₁ ^Ala.