THE AMINOACYL-TRANSFER RNA-SYNTHETASE FAMILY - MODULES AT WORK

The combined use of molecular and structural biology techniques has pr oved very efficient in elucidating structure-function relationships in aminoacyl-tRNA synthetases. Our present understanding of this family of enzymes is based on two main unifying principles: (i) division into two different classes, corresponding to two different modes of ATP bi nding and attachment of the activated amino acid to the last nucleotid e of tRNA (either 2'OH or 3'OH of the ribose) by two different catalyt ic mechanisms and two structural domains with completely different fol ding, and (ii) the modular organization into separate and additional d omains that we are just beginning to understand. Sequence analysis com plements very nicely existing structural, biochemical and genetic resu lts and makes them more general, leading to verifiable predictions.