Mammalian high-molecular-weight and monomeric forms of valyl-tRNA synthetase

Valyl-tRNA synthetase from rat liver sediments at 15.5 S with a Stokes radius of 90 A, corresponding to a native molecular weight of 585,000. Purification of valyl-tRNA synthetase to homogeneity by a combination of conventional and affinity column chromatography yields a fully active monomeric form...

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Bibliographic Details
Published in:Biochemistry (Easton) 1988-03, Vol.27 (6), p.2181-2186
Main Authors: Godar, Y. Dianne, Yang, David C. H
Format: Article
Language:English
Subjects:
Amino Acyl-tRNA Synthetases - isolation & purification
Analytical, structural and metabolic biochemistry
Animals
Biological and medical sciences
Centrifugation, Density Gradient
Chromatography, Affinity
Chromatography, Gel
Enzymes and enzyme inhibitors
Fundamental and applied biological sciences. Psychology
Kinetics
Ligases
Liver - enzymology
Macromolecular Substances
Molecular Weight
Protein Conformation
Rats
Thermodynamics
Valine-tRNA Ligase - isolation & purification
Valine-tRNA Ligase - metabolism
valyl-tRNA synthetase
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Summary:Valyl-tRNA synthetase from rat liver sediments at 15.5 S with a Stokes radius of 90 A, corresponding to a native molecular weight of 585,000. Purification of valyl-tRNA synthetase to homogeneity by a combination of conventional and affinity column chromatography yields a fully active monomeric form of valyl-tRNA synthetase with a sedimentation coefficient of 7.7 S and a Stokes radius of 45 A. The subunit molecular weight of the monomeric valyl-tRNA synthetase is 140,000, as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. In the presence of 400 mM KCl, the purified monomeric valyl-tRNA synthetase associates to a high molecular weight form. The high molecular weight valyl-tRNA synthetase in the homogenate can be readily converted to the monomeric form by controlled trypsinization. The kinetic parameters of the two forms are nearly identical. The results suggest that the high molecular weight valyl-tRNA synthetase is a homotypic tetramer and converts to the monomeric valyl-tRNA synthetase after the cleavage of a small peptide.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00406a055