The Subunit Structure of Phenylalanyl‐tRNA Synthetase of <i>Escherichia coli</i>

Abstract

Fingerprints of tryptic digests of phenylalanyl‐tRNA synthetase of Escherichia coli NP 3 suggest that the smallest identical subunit is one fourth of the size of the native protein (mol. wt. 181000). Determination of the subunit size by gel electrophoresis reveals a molecular weight of 43000 ± 2000. By the criteria employed the enzyme therefore seems to be composed of four identical subunits. Phenylalanyl‐tRNA synthetase which has been denatured by treatment with 8 M urea is able to reform active enzyme indistinguishable by its size from the native protein. Again, a size of about 45000 was determined for the subunits active in the association reaction.