Subunit Structure of the Methionine‐Repressible Aspartokinase II–Homoserine Dehydrogenase II from Escherichia coli K12

Abstract

The quaternary structure of Escherichia coli K 12 aspartokinase II–homoserine dehydrogenase II has been examined. This multifunctional protein has a molecular weight M_r= 176000. It is composed of two subunits having the same molecular weight and the same charge. The results obtained from the examination of tryptic maps, the number and amino acid composition of cysteine‐containing peptides and the uniqueness of the N‐terminal sequence, strongly suggest that the 2 subunits are identical. The properties of aspartokinase II–homoserine dehydrogenase II can be compared to those of the much better known protein aspartokinase I–homoserine dehydrogenase I.