This family is found in bacteria and archaea, and is approximately 100 amino acids in length. There is a conserved NGPCGG sequence motif. This family is the C terminal of methylene-tetrahydrofolate reductase. This protein reduces FAD using the reducing equivalents from reduced FAD, subsequently reduces tetrahydrofolate. The C terminal of MTHFR contains the FAD binding site and is the catalytic portion of the enzyme.