Comparison of amino acid polymerization factors isolated from rat liver and rabbit reticulocytes

Abstract

Using preliminary ammonium sulfate fractionation followed by calcium phosphate adsorption and elution, two complementary fractions, T 1 and T 2, analogous to Schweet's TF-1 and TF-2, were obtained from liver as well as reticulocytes. In both cases, a further separation of the two fractions was achieved by DEAE-cellulose column adsorption and elution with a potassium chloride gradient. The prepurified liver fractions were also identified as T 1 and T 2, respectively, after Sephadex G-200 chromatography. Cross complementation was obtained between T 1 and T 2 derived from either source. A ribosome-linked GTPase partly coincided with the T 2 fraction but did not respond to the addition of template or aminoacyl-sRNA. The T 1 fraction catalyzed GTP-linked binding of aminoacyl-sRNA to template-charged ribosomes, and GTP hydrolysis was observed coincident with the T 1-linked binding of aminoacyl-sRNA to the ribosome but exceeded the binding reaction about 20-fold. The binding assay was performed in the absence of a sulfhydryl compound to prevent polymerization. The T 2 function was not studied in detail, except that it caused polymerization when added to the T 1 system together with a sulfhydryl compound. A common nomenclature is proposed, and a separation procedure that is generally applicable to mammalian cell extractions is presented.