http://hoffman.cm.utexas.edu/courses/wood_lungdahl_1.pdf

Acetogenesis and the Wood-Ljungdahl Pathway of CO2 Fixation

DNA methylation, an essential epigenetic feature of DNA that modulates gene expression and genomic integrity, is catalyzed by methyltransferases that use the universal methyl donor S-adenosyl-l-methionine. Methylenetetrahydrofolate reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate (5-methylTHF), the methyl donor for synthesis of methionine from homocysteine and precursor of S-adenosyl-l-methionine. In the present study we sought to determine the effect of folate status on genomic DNA methylation with an emphasis on the interaction with the common C677T mutation in the MTHFR gene. A liquid chromatography/MS method for the analysis of nucleotide bases was used to assess genomic DNA methylation in peripheral blood mononuclear cell DNA from 105 subjects homozygous for this mutation (T/T) and 187 homozygous for the wild-type (C/C) MTHFR genotype. The results show that genomic DNA methylation directly correlates with folate status and inversely with plasma homocysteine (tHcy) levels (P < 0.01). T/T genotypes had a diminished level of DNA methylation compared with those with the C/C wild-type (32.23 vs.62.24 ng 5-methylcytosine/μg DNA, P < 0.0001). When analyzed according to folate status, however, only the T/T subjects with low levels of folate accounted for the diminished DNA methylation (P < 0.0001). Moreover, in T/T subjects DNA methylation status correlated with the methylated proportion of red blood cell folate and was inversely related to the formylated proportion of red blood cell folates (P < 0.03) that is known to be solely represented in those individuals. These results indicate that the MTHFR C677T polymorphism influences DNA methylation status through an interaction with folate status.

https://www.pnas.org/content/pnas/99/8/5606.full.pdf

A common mutation in the 5,10-methylenetetrahydrofolate reductase gene affects genomic DNA methylation through an interaction with folate status

The Biomarkers of Nutrition for Development (BOND) project is designed to provide evidence-based advice to anyone with an interest in the role of nutrition in health. Specifically, the BOND program provides state-of-the-art information and service with regard to selection, use, and interpretation of biomarkers of nutrient exposure, status, function, and effect. To accomplish this objective, expert panels are recruited to evaluate the literature and to draft comprehensive reports on the current state of the art with regard to specific nutrient biology and available biomarkers for assessing nutrients in body tissues at the individual and population level. Phase I of the BOND project includes the evaluation of biomarkers for 6 nutrients: iodine, iron, zinc, folate, vitamin A, and vitamin B-12. This review represents the second in the series of reviews and covers all relevant aspects of folate biology and biomarkers. The article is organized to provide the reader with a full appreciation of folate's history as a public health issue, its biology, and an overview of available biomarkers (serum folate, RBC folate, and plasma homocysteine concentrations) and their interpretation across a range of clinical and population-based uses. The article also includes a list of priority research needs for advancing the area of folate biomarkers related to nutritional health status and development.

/pdf/biomarkers-of-nutrition-for-development-bond-iron-review-4ibc6okj7y.pdf

Biomarkers of Nutrition for Development (BOND)-Iron Review.

Folic acid: nutritional biochemistry, molecular biology, and role in disease processes.

Determinants of plasma total homocysteine concentration in the Framingham Offspring cohort

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.

/pdf/the-structure-and-properties-of-methylenetetrahydrofolate-44t1jiicwb.pdf

The structure and properties of methylenetetrahydrofolate reductase from Escherichia coli suggest how folate ameliorates human hyperhomocysteinemia.

In human methylenetetrahydrofolate reductase (MTHFR) the Ala222Val (677C-->T) polymorphism encodes a heat-labile gene product that is associated with elevated levels of homocysteine and possibly with risk for cardiovascular disease. Generation of the equivalent Ala to Val mutation in Escherichia coli MTHFR, which is 30% identical to the catalytic domain of the human enzyme, creates a protein with enhanced thermolability. In both human and E. coli MTHFR, the A --> V mutation increases the rate of dissociation of FAD, and in both enzymes, loss of FAD is linked to changes in quaternary structure [Yamada, K., Chen, Z., Rozen, R., and Matthews, R. G. (2001) Proc. Natl. Acad. Sci. U.S.A. 98, 14853-14858; Guenther, B. D., Sheppard, C. A., Tran, P., Rozen, R., Matthews, R. G., and Ludwig, M. L. (1999) Nat. Struct. Biol. 6, 359-365]. Folates have been shown to protect both human and bacterial enzymes from loss of FAD. Despite its effect on affinity for FAD, the A --> V mutation is located at the bottom of the (betaalpha)(8) barrel of the catalytic domain in a position that does not contact the bound FAD prosthetic group. Here we report the structures of the Ala177Val mutant of E. coli MTHFR and of its complex with the 5,10-dideazafolate analogue, LY309887, and suggest mechanisms by which the mutation may perturb FAD binding. Helix alpha5, which immediately precedes the loop bearing the mutation, carries several residues that interact with FAD, including Asn168, Arg171, and Lys172. In the structures of the mutant enzyme this helix is displaced, perturbing protein-FAD interactions. In the complex with LY309887, the pterin-like ring of the analogue stacks against the si face of the flavin and is secured by hydrogen bonds to residues Gln183 and Asp120 that adjoin this face. The direct interactions of bound folate with the cofactor provide one mechanism for linkage between binding of FAD and folate binding that could account in part for the protective action of folates. Conformation changes induced by folate binding may also suppress dissociation of FAD.

/pdf/structural-perturbations-in-the-ala-val-polymorphism-of-4lets14te2.pdf

Structural perturbations in the Ala --> Val polymorphism of methylenetetrahydrofolate reductase: how binding of folates may protect against inactivation.

Brian D. Guenther

Papers

The structure and properties of methylenetetrahydrofolate reductase from Escherichia coli suggest how folate ameliorates human hyperhomocysteinemia.

Structural perturbations in the Ala --> Val polymorphism of methylenetetrahydrofolate reductase: how binding of folates may protect against inactivation.

Escherichia coli methylenetetrahydrofolate reductase