A novel function of Escherichia coli transfer RNA nucleotidyltransferase. Biosynthesis of the C-C-A sequence in a phage T4 transfer RNA precursor.

Fj Schmidt

doi:10.1016/s0021-9258(19)40771-0

Abstract

The biosynthesis of the phage T4-coded proline and serine transfer RNA species proceeds through a precursor RNA containing both tRNA sequences. Neither tRNA sequence in the precursor RNA contains the 3'-terminal C-C-A common to all mature tRNAs. Seidman and McClain ((1975) Proc. Natl. Acad. Sci. U. S. A. 72, 1491-1495) have proposed that the C-C-A sequence is added to serine tRNA while it is still part of the large precursor RNA. In the present work, I show that, in vitro, a purified preparation of Escherichia coli tRNA nucleotidyltransferase (EC 2.7.7.25) accurately synthesized 3'-terminal C-C-A in the serine tRNA portion of the precursor RNA. This result establishes a role of tRNA nucleotidyltransferase in the biosynthesis of the phage T4 serine tRNA. The finding that tRNA nucleotidyltransferase utilizes the large precursor RNA as a substrate represents a novel function of the enzyme.

Highlights

The biosynthesis of the phage T4-coded proline and serine transfer RNA species proceeds through a precursor RNA containing both tRNA sequences
A. 72, 1491-1495) have proposed that the C-C-A sequence is added to serine tRNA while it is still part of the large precursor RNA
I show that, in uitro, a purified preparation of Escherichia coli tRNA nucleotidyltransferase (EC 2.7.7.25) accurately synthesized 3’-terminal C-C-A in the serine tRNA portion of the precursor RNA. This result establishes a role of tRNA nucleotidyltransferase in the biosynthesis of the phage T4 serine tRNA

Summary

A Novel Function of Escherichia coZi Transfer RNA Nucleotidyltransferase

From sequence analyses of precursor RNAs which accumulate after infection of mutant Escherichia coli strains blocked in tRNA biosynthesis, Seidman and McClain [6] have concluded that the C-C-A sequence is added to the serine tRNA species prior to cleavage by ribonuclease P These in viuo results, do not unambiguously define the enzymatic requirements for tRNA biosynthesis. Phage T4 serine tRNA biosynthesis requires similar in vitro reconstructions of all the steps in the pathway In this communication, I report the first phase of these experiments: E. coli tRNA nucleotidyltransferase accurately synthesized the C-C-A sequence in a tRNA precursor. This finding represents the first demonstration of a biosynthetic role of the enzyme

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RESULTS

F J Schmidt