(adapted from investigator's abstract): This proposal will investigate a number of unique components of the archael translation apparatus which are essential for the faithful decoding of mRNA into protein. Correctly amino- aceylated tRNAs are required for accurate ribosomal translation. They are generally believed to be provided solely by the aminoacyl-tRNA synthetases, a ubiquitous and highly conserved family of enzymes found throughout the living kingdom. However, many organisms and some organelles lack at least one aminoacyl-tRNA synthetase, glutaminyl-tRNA synthetase. In these organisms and organelles Gln-tRNA is formed by the amidation of glutamate mis acylated to t-RNA Gln. The P.I. has recently shown that a comparable pathway also exists for the synthesis of Asn-tRNA in Archaea. Thus amino acid transformations, previously only associated with intermediary metabolism, are a key requirement for translational fidelity particularly in Archaea. A second unique feature of archael aminoacyl-tRNA formation is the use of enzymes distinct from any yet found in either eubacteria or eukaryotes to generate lysyl-tRNA and cysteinyl-tRNA.