Binding of [ 14 C]Erythromycin to Escherichia coli Ribosomes

Abstract

Erythromycin binding to Escherichia coli ribosomes required K ⁺ and Mg ²⁺ . Under optimal conditions, the dissociation constant for erythromycin binding to E. coli ribosomes was found to be 1.0 × 10 ⁻⁸ M and 1.4 × 10 ⁻⁸ M at 24 C and 5 C, respectively. One molecule of [ ¹⁴ C]erythromycin was bound to each 70 S ribosome at equilibrium. Binding of erythromycin to ribosomes was rapid and reversible. The specific rate constants for the forward and reverse reactions were 1.7 × 10 ⁷ liters per mol per min and 0.15 per min, respectively.