CONTENTS INTRODUCTION ............................................................................................................ 806 THE MULTIPLE BIOLOGICAL FUNCTIONS F tRNA ................................................ 807 tRNA Cycle in Protein Synthesis .............................................................................. 807 tRNA and the Regulation of Enzyme Synthesis ............

Many bacteria lack genes encoding asparaginyl- and/or glutaminyl-tRNA synthetase and consequently rely on an indirect path for the synthesis of both Asn-tRNA(Asn) and Gln-tRNA(Gln). In some bacteria such as Thermus thermophilus, efficient delivery of misacylated tRNA to the downstream amidotransferase (AdT) is ensured by formation of a stable, tRNA-dependent macromolecular complex called the As...

Aminoacylation of transfer RNA(Gln) (tRNA(Gln)) is performed by distinct mechanisms in different kingdoms and represents the most diverged route of aminoacyl-tRNA synthesis found in nature. In Saccharomyces cerevisiae, cytosolic Gln-tRNA(Gln) is generated by direct glutaminylation of tRNA(Gln) by glutaminyl-tRNA synthetase (GlnRS), whereas mitochondrial Gln-tRNA(Gln) is formed by an indirect pa...

Aminoacyl-tRNA synthetases are modular enzymes composed of a central active site domain to which additional functional domains were appended in the course of evolution. Analysis of bacterial genome sequences revealed the presence of many shorter aminoacyl-tRNA synthetase paralogs. Here we report the characterization of a well conserved glutamyl-tRNA synthetase (GluRS) paralog (YadB in Escherich...

Cysteinyl-tRNA (Cys-tRNA) is essential for protein synthesis. In most organisms the enzyme responsible for the formation of Cys-tRNA is cysteinyl-tRNA synthetase (CysRS). The only known exceptions are the euryarchaea Methanococcus jannaschii and Methanobacterium thermoautotrophicum, which do not encode a CysRS. Deviating from the accepted concept of one aminoacyl-tRNA synthetase per amino acid,...

A highly sensitive assay of tRNA aminoacylation was developed that directly measures the fraction of aminoacylated tRNA by following amino acid attachment to the 3'-(32)P-labeled tRNA. When applied to Escherichia coli alanyl-tRNA synthetase, the assay allowed accurate measurement of aminoacylation of the most deleterious mutants of tRNA(Ala). The effect of tRNA(Ala) identity mutations on both a...

Yeast Los1p, the homolog of human exportin-t, mediates nuclear export of tRNA. Using fluorescence in situ hybridization, we could show that the export of some intronless tRNA species is not detectably affected by the disruption of LOS1. To find other factors that facilitate tRNA export, we performed a suppressor screen of a synthetically lethal los1 mutant and identified the essential translati...

Antibodies with specificity to a single species of tRNA were elicited in a goat by immunization with a glutaraldehyde conjugate of yeast phenylalanine transfer RNA with bovine gamma globulin. The specificity of the antibodies was studied by a radioimmunoassay measuring the direct binding of [(3)H]tRNA(Phe) or the inhibition of the binding. The antibodies formed are predominantly directed toward...

Retroviral reverse transcription is initiated from a cellular tRNA molecule and all known exogenous isolates of murine leukemia virus utilise a tRNA(Pro)molecule. While several studies suggest flexibility in murine leukemia virus primer utilisation, studies on human immunodeficiency virus and avian retro-viruses have revealed evidence of molecular adapt-ation towards the specific tRNA isoaccept...

tRNA biosynthesis in the eukaryotic cell is a multistep pathway, involving transcription, 5' and 3' end maturation, intron removal, and numerous modifications of nucleotides. Most of the genes coding for each of the elements essential for tRNA biosynthetic activities were primarily identified by genetic selection in yeast [1]. In these studies, the parental strain contained a tRNA gene that had...