Arginyl‐tRNA Synthetase from Baker's Yeast. Purification and Some Properties

Abstract

Arginyl‐tRNA synthetase from baker's yeast (Saccharomyces cerevisiae, strain 836) was obtained pure by a large‐scale preparative method, which involves four chromatographic columns and one preparative polyacrylamide gel electrophoretic step. The enzyme has a high specific activity (9000 U/ mg) and consists of a single polypeptide chain of molecular weight approximately 73000 as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate. Amino acid analysis of the enzyme permitted calculation of the absorption coefficient of arginyl‐tRNA synthetase (A1 mg /ml280 nm= 1.26). Concerning kinetic parameters of the enzyme we found the following Km values: 0.28 μM, 300 μM, 1.5 μM for tRNAArg111, ATP and arginine in the aminoacylation reaction, and 1400 μM, 2.5 μM, and 50 μM for ATP, arginine and PPi in the ATP‐PPi exchange reaction. Arginyl‐ tRNA synthetase requires tRNAArg111 to catalyse the ATP‐PPi exchange reaction. Copyright © 1976, Wiley Blackwell. All rights reserved