Folate-cobalamin interaction

Fig. 1. Folate-cobalamin interaction in the synthesis of purines and pyrimidines and, therefore, of DNA. (1) In gastrointestinal mucosa cells (2) in the liver (3) in peripheral tissues. C, cobalamine DAC, desoxyadenosylcobalamine HC, hydroxy cobalamine MC, methylcobalamine F, folic acid MTHF, methyltetrahydrofolic acid THF, tetrahydrofolic acid DHF, dihydrofolic acid dUMP, deoxyuridinemonophosphate dTMP, deoxythymidine-monophosphate. (Adapted from Far-...

Savage DG, Lindenbaum J. Folate-cobalamin interactions. In Bailey LB, editor. Folate in Health and Disease. New York Marcel Dekker Inc, 1994 237-85. 

Figure 3. Three of the modules comprising methionine synthase. At the top center is the Bi2- binding fragment [651-896], a structure with two domains, one a four-helix bundle that serves to cap the cofactor, and the other an a/p fold that interacts with the lower face of the corrin macrocycle and binds the nucleotide tail of cobalamin. Measurements of the rates of photolysis of the C0-CH3 bond indicate that the cap domain covers the upper face of the corrin in the substrate-free form of the intact enzyme (7). On the lower right is the activation domain [897-1227] with bound AdoMet. This helmet-shaped single domain is an unusual fold with no resemblance to other well-characterized AdoMet-binding domains (8). On the lower left is the structure of the methyltransferase AcsE from Moorella thermoaceticum, which we take as a surrogate for the folate-binding domain of MetH.

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