Mutational Alteration of the Maximal Level of Lac Operon Expression

Abstract

The enzymes of a bacterial cell are present in widely different amounts, as judged by their activities and, in some cases, by direct measurement of the number of molecules (for discussion see Pardee and Beckwith, 1962). Such variation is due partly to the regulation of repressible gene-systems. However, variation is also observed in the activities of enzymes coded by different genes under conditions of full induction. This may be an effect of differences in enzyme efficiency or of the maximal rate at which an enzyme can be produced. In this paper, we wish to discuss the genetic control of the maximum rate of enzyme production.