Nucleotide sequence of the metL gene of Escherichia coli. Its product, the bifunctional aspartokinase ii-homoserine dehydrogenase II, and the bifunctional product of the thrA gene, aspartokinase I-homoserine dehydrogenase I, derive from a common ancestor.

The total nucleotide sequence (2427 nucleotides) of the metL gene ofEscherichia coli coding for the dimeric aspartokinase Il-homoserine dehydrogenase II (809 amino acid residues, M, = 88,726jchain) is presented.Comparison of the translated sequence with that of aspartokinase I-homoserine dehydrogenase I, the product of the thrA gene of the same organism, shows that the two proteins are highly homologous and that they derive from a common ancestor.