Regulation of cessation of early enzyme synthesis in bacteriophage T4 infected Escherichia coli: Separate mechanisms for different enzymes

Abstract

The kinetics of synthesis of four early enzymes (deoxycytidine triphosphatase, deoxycytidylate hydroxymethylase, deoxynucleotide kinase and thymidylate synthetase) were studied in bacteriophage T4-infected Escherichia coli B207. E. coli B207 is a mutant of E. coli B which is defective in the accumulation and retention of K+ from the growth medium. In mutant cells depleted of K+, the rate of protein synthesis can be regulated by the level of this cation in the growth medium. When bacteriophage T4 infected E. coli B207 cells were incubated in normal growth medium (i.e., containing 33 m M K+), the kinetics of synthesis of the four enzymes studied were identical. However, when infected B207 cells were allowed to synthesize protein at 50% the normal rate (in medium containing 1 m M K+) it was possible to subdivide the four early enzymes into three separate classes based on their kinetics of synthesis. Deoxycytidine triphosphatase and deoxycytidylate hydroxymethylase proved to be members of the same class of early enzyme, while deoxynucleotide kinase and thymidylate synthetase were found to be members of a second and third class, respectively.