Purification of cytoplasmic precursors of yeast mitochondrial phenylalanyl-tRNA synthetase subunits.

Two polypeptidic precursors of yeast mitochondrial phenylalanyl-tRNA synthetase subunits were purified from the cytoplasm by immunoprecipitation with an insolubilized glutaraldehyde-treated IgG fraction, followed by two chromatographies on Sephadex G-200 and on DEAE-cellulose. Methionine was found as the N-terminal residue in both precursors, which exhibited N-terminal extensions.