Revised structure of aspartokinase I-homoserine dehydrogenase I of Escherichia coli K12. Evidence for four identical subunits.

Abstract

After revision, the molecular weight of the subunit of Escherichia coli K12 aspartokinase I‐homoserine dehydrogenase I is 86000 ± 4000 instead of 60000 as previously published. The enzyme is a tetramer, not an hexamer. The electrophoretic homogeneity of the subunits, the number of unique sequences around cysteinyl and tryptophanyl residues, the determination of the N‐terminal and C‐terminal sequences all point to the probable identity of the four subunits.After revision of the molecular absorption coefficient, a new set of binding data for various ligands of the enzyme is given.