The Structure and Properties of Methylenetetrahydrofolate Reductase From Escherichia Coli Suggest How Folate Ameliorates Human Hyperhomocysteinemia

Nat Struct Biol. 1999 Apr;6(4):359-65. doi: 10.1038/7594.

Abstract

Elevated plasma homocysteine levels are associated with increased risk for cardiovascular disease and neural tube defects in humans. Folate treatment decreases homocysteine levels and dramatically reduces the incidence of neural tube defects. The flavoprotein methylenetetrahydrofolate reductase (MTHFR) is a likely target for these actions of folate. The most common genetic cause of mildly elevated plasma homocysteine in humans is the MTHFR polymorphism A222V (base change C677-->T). The X-ray analysis of E. coli MTHFR, reported here, provides a model for the catalytic domain that is shared by all MTHFRs. This domain is a beta8alpha8 barrel that binds FAD in a novel fashion. Ala 177, corresponding to Ala 222 in human MTHFR, is near the bottom of the barrel and distant from the FAD. The mutation A177V does not affect Km or k(cat) but instead increases the propensity for bacterial MTHFR to lose its essential flavin cofactor. Folate derivatives protect wild-type and mutant E. coli enzymes against flavin loss, and protect human MTHFR and the A222V mutant against thermal inactivation, suggesting a mechanism by which folate treatment reduces homocysteine levels.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Binding Sites
  • Escherichia coli / enzymology*
  • Flavin-Adenine Dinucleotide / metabolism
  • Folic Acid / metabolism*
  • Folic Acid / pharmacology
  • Humans
  • Hyperhomocysteinemia / enzymology*
  • Methylenetetrahydrofolate Reductase (NADPH2)
  • Models, Molecular
  • Molecular Sequence Data
  • Mutation
  • Oxidoreductases Acting on CH-NH Group Donors / chemistry*
  • Oxidoreductases Acting on CH-NH Group Donors / genetics*
  • Oxidoreductases Acting on CH-NH Group Donors / metabolism
  • Polymorphism, Genetic
  • Protein Conformation
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Structure-Activity Relationship
  • X-Ray Diffraction

Substances

  • Bacterial Proteins
  • Recombinant Proteins
  • Flavin-Adenine Dinucleotide
  • Folic Acid
  • Oxidoreductases Acting on CH-NH Group Donors
  • Methylenetetrahydrofolate Reductase (NADPH2)

Associated data

  • PDB/1B5T