LIGASE, ROSSMANN FOLD, AMINOACYL-TRNA SYNTHETASE, ATP-BINDING, CYTOPLASM, METAL-BINDING, NUCLEOTIDE-BINDING, PROTEIN BIOSYNTHESIS, RNA-BINDING, TRNA-BINDING, ZINC 3H9B STRUCTURE OF A MUTANT METHIONYL-TRNA SYNTHETASE WITH MODIFIED SPECIFICITY COMPLEXED WITH AZIDONORLEUCINE