The primary structure of Lactobacillus casei thymidylate synthetase. II. The complete amino acid sequence of the active site peptide, CNBr 4.

The 102 amino acid residues of CNBr 4, the largest of 5 cyanogen bromide peptides from the Lactobacillus casei thymidylate synthetase were completely sequenced by means of limited tryptic, tryptic, chymotryptic, and staphylococcal protease peptides. CNBr 4 contains both of the cysteines in an enzyme subunit, with the 5-fluorodeoxyuridylate-reactive cysteine at residue 198 and the other at residue 244.