Tryptophanyl Transfer Ribonucleic Acid Synthetase of Escherichia coli

The molecular weight of tryptophanyl-tRNA synthetase of Escherichia coli is 74,000 by Sephadex gel filtration and 81,000 by sucrose gradient centrifugation. Both sodium dodecyl sulfate polyacrylamide gel electrophoresis and agarose gel filtration in 8 m urea reveal subunits of 37,000 in molecular weight. In addition only one protein band is observed after polyacrylamide disc gel electrophoresis in the presence if 8 m urea. By these criteria the...