COORDINATE VARIATIONS IN INDUCED SYNTHESES OF ENZYMES ASSOCIATED WITH MUTATIONS IN A STRUCTURAL GENE

Abstract

Mutations located at different sites in the L-ribulokinase structural gene cause coordinated increases or decreases in the syntheses of L-arabinose isomerase, L-ribulose 5-phosphate 4-epimerase, and L-ribulokinase CRM. The possibility of this dual function of a structural gene being caused by altered enzymes, altered internal concentration of L- arabinose and cytoplasmic inhibitors, or inducers all appear to have been ruled out. It thus appears that the rate of enzyme synthesis is not solely determined by regulatory genes of the i type but the coding of the structural gene may set the limits in the rates of synthesis of one or more enzymes specified in a "genetic unit of coordinate expression".