Macromolecular complexes from sheep and rabbit containing seven aminoacyl-tRNA synthetases. II. Structural characterization of the polypeptide components and immunological identification of the methionyl-tRNA synthetase subunit.

摘要: The extensively purified multienzyme complexes from sheep and rabbit livers containing seven aminoacyl-tRNA synthetases specific for Ile, Leu, Met, Gln, Glu, Lys, Arg displayed characteristic one-dimensional sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoretic patterns composed of 11 10 major polypeptide components, respectively. Their compositions revealed by two-dimensional electrophoresis, including isoelectric focusing in 9 M urea, were not significantly more complex. point each component the two fell within pH range 6.2 to 7.1, with notable exception common Mr = 43,000 which was distinctly basic. apparent molecular weight both determined SDS-polyacrylamide electrophoresis. Four polypeptides, corresponding weights 139,000, 129,000, 43,000, 38,000 complexes. other components similar yet clearly distinct weights. molar ratios estimated densitometry scanning stained gels, indicated that several complex may be present as than one copy. Following methionyl-tRNA synthetase identified protein blotting procedure, using antibodies 125I-labeled A. unique labeled bands precisely matched polypeptides 103,000 108,000, Mild trypsin treatment native generated fully active forms synthetase, 68,000 69,500, kinetics proteolysis showed modification proceeded sequentially through discrete intermediates.