The characterization of lysine transfer RNA and lysyl-tRNA synthetase from germinating barley endosperms

Lysine tRNA and lysyl-tRNA synthetase were studied in barley (Hordeum vulgare L. cv. Atlas 57) endosperm. Six isoaccepting species of lysine tRNA were present in all tissues examined. RPC-5 chromatography revealed no differences in the lysine tRNA profiles from embryo-less half-seeds, starchy endosperm and isolated aleurone layers. Lysine tRNA profiles did not change during the first 48 hours of germination, in embryo-less half-seeds incubated in the presence and absence of gibberellic acid. The lysine analog S-2-aminoethyl-Lcysteine (AEC) was shown to be a competitive inhibitor of lysine in the lysyl-tRNA synthetase reaction. The Km and Ki values for lysine and AEC were determined to be in the micromolar range. The usefulness of the parameters measured and the methods developed for the characterization of amino acid analog-resistant mutants is discussed.