HIGHER SPECIFIC ACTIVITY OF THE ESCHERICHIA-COLI GLUTAMYL-TRANSFER RNA-SYNTHETASE PURIFIED TO HOMOGENEITY BY A 6-HOUR PROCEDURE

The glutamyl-tRNA synthetase (EC 6.1.1.17) of Escherichia coli was purified to homogeneity from the overproducing strain DH5α(pLQ7612) by a two-step procedure that takes only about 6 h and yields 10 mg of enzyme per gram of wet cells. The process consists of a two-phase polyethylene glycol-dextran partition, the top phase of which is diluted and directly applied to an anion-exchange FPLC MonoQ column. The purified enzyme has a specific activity about twice that of the same enzyme purified to homogeneity by the lengthy conventional procedure from either a normal strain or this overproducing strain. This difference is discussed in relation to the generation of microheterogeneity in proteins during their purification. © 1992 Academic Press, Inc.