Some Physical Parameters of Succinyl-Coenzyme A Synthetase of Escherichia coli

Abstract

A physical study of succinyl-coenzyme A synthetase of Escherichia coli has been conducted. The extinction coefficient for the enzyme at 280 nm [Formula: see text] has been evaluated by two independent methods and found to be equal to 4.9 ± 0.2. Sedimentation equilibrium studies show that there is a marked dependence of the apparent molecular weight upon the concentration of the enzyme. At concentrations above 1 mg/ml, the enzyme exists predominantly as an α2β2 tetramer of overall molecular weight near 140 000; at lower concentrations, a significant fraction of the enzyme dissociates to an αβ dimer. The circular dichroism spectrum of the enzyme suggests a high proportion of random coil structure, with small contributions of α-helix and β-structure.