Studies on Polypeptide Elongation Factor from E. coli

Abstract

The ribosome-dependent guanosine triphosphatase (Elongation Factor G) has been purified from Escherichia coli by protamine precipitation, ammonium sulfate fraction-ation, DEAE-Sephadex column chromatography, gel filtration through Sephadex G-200, and second DEAE-Sephadex column chromatography. The purified factor G was crystallized in the form of needles by addition of ammonium sulfate. The crystalline factor G appears to be homogeneous as judged from ultracentrifugation and gel elec-trophoresis. The sedimentation coefficient of factor G is 4.5 S (s^o₂₀, W) and the molecular weight as determined from the equilibrium centrifugation is 83,000. Factor G catalyzes the ribosome-dependent hydrolysis of GTP in the absence of messenger RNA and amino-acyl-tRNA (the uncoupled GTPase reaction). Some properties of the uncoupled GTPase reaction are described.