Abstract
Asparagine synthetase purified from rat liver reveals two species (slower migrating band I and faster migrating band II) when subjected to polyacrylamide gel electrophoresis under nondenaturing conditions (S. Hongo and T. Sato (1981) Anal. Biochem. 114, 163–166). We have investigated some molecular properties of these species. Elution of band I from the gel and re-electrophoresis showed that band I yielded band II similar to that of the initial run. Peptide maps by limited proteolysis were very similar and amino acid compositions were also alike in the two species. l-Lysine was identified as the sole NH 2-terminal amino acid in both the species. By cross-linking experiments the enzyme was shown to be a dimeric protein. When the purified enzyme was subjected to isoelectric focusing the enzyme activity and protein focused at pH 6.0 in a single peak. These results demonstrate that rat liver asparagine synthetase is composed of two identical subunits. The enzyme, inactivated by storage at −20°Cfor about 3 months, showed aggregated forms in polyacrylamide gel electrophoresis, and was reactivated markedly by the addition of dithiothreitol.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular Enzymology
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