Immunological crossreactivity of eukaryotic C1-tetrahydrofolate synthase and prokaryotic 10-formyltetrahydrofolate synthetase.

Antiserum to yeast C1-tetrahydrofolate (C1-H4folate) synthase reacts with other eukaryotic C1-H4folate synthases and prokaryotic 10-formyltetrahydrofolate (10-CHO-H4folate) synthetases [formate:tetrahydrofolate ligase (ADP-forming), EC 6.3.4.3] even though these enzymes vary in subunit size and function and probably vary widely in sequence. The comigration of the purified enzymes with the immunoreactive material establishes the specificity of the reaction for C1-H4folate synthase proteins. Reciprocal crossreaction of the antibody to Clostridium acidiurici 10-CHO-H4folate synthetase with the eukaryotic proteins indicates that such broad cross-species reactions are not specific to the antisera elicited in response to the yeast C1-H4folate synthase. These specific crossreactions among divergent species have been observed only on an electrophoretic transfer blot of a denaturing polyacrylamide gel. These observations may have been possible because of the sensitivity and specificity of the technique, which differ from more conventional immunochemical methods.