Identification of amino acid residues, essential for maintaining the tetrameric structure of sheep liver cytosolic serine hydroxymethyltransferase, by targeted mutagenesis.

Serine hydroxymethyltransferase (SHMT), a pyridoxal 5'-phosphate (PLP)-dependent enzyme, catalyses the transfer of the hydroxymethyl group from serine to tetrahydrofolate to yield glycine and N (5), N (10)-methylenetetrahydrofolate. An analysis of the known SHMT sequences indicated that several amino acid residues were conserved. In this paper, we report the identification of the amino acid residues essential for maintaining the oligomeric structure of sheep liver cytosolic recombinant SHMT (scSHMT) through intra- and inter-subunit interactions and by stabilizing the binding of PLP at the active site.