Aspartate Transcarbamylase. Amino-Terminal Analyses and Peptide Maps of the Subunits^*

Abstract

suggests that there are four each of the two different kinds of peptide chains in the native enzyme (molecular weight 3.1 X 10s). Taken together with the data of Changeux et al. (Changeux, J.-P., Gerhart, J. C., and Schachman, . K. (1967), in Regulation of Nucleic Acid and Protein Biosynthesis, Koningsberger, V. V., and Bosch, L, Ed., New York, N. Y., Elsevier, p 344) our results indicate that each of the binding sites for succinate (a competitive inhibitor of aspartatate) and cytidine triphosphate resides on a separate chain.

Regulation of Purine and Pyrimidine Metabolism

“…Independent confirmation of the tetramer configuration was obtained by other investigators [99,100] through methods of MW determination in urea, amino-terminal residues, and peptide analysis. However, a further probing by Weber [101], through subunit determination after denaturation with sodium dodecylsulfate, analysis of carboxy-terminal residues, and a proposed amino acid sequence for the R chain, has led to a rejection of the tetramer model in favor of a hexamer.…”