1a4i
HUMAN TETRAHYDROFOLATE DEHYDROGENASE / CYCLOHYDROLASEHUMAN TETRAHYDROFOLATE DEHYDROGENASE / CYCLOHYDROLASE
Structural highlights
Disease[C1TC_HUMAN] Defects in MTHFD1 may be a cause of susceptibility to folate-sensitive neural tube defects (FS-NTD) [MIM:601634]. The most common NTDs are open spina bifida (myelomeningocele) and anencephaly. Genetic defects in MTHFD1 may affect the risk of spina bifida via the maternal rather than the embryonic genotype.[1] [2] [3] Genetic variation in MTHFD1 could be associated with susceptibility to colorectal cancer (CRC) [MIM:114500]. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBACKGROUND: The interconversion of two major folate one-carbon donors occurs through the sequential activities of NAD(P)-dependent methylene[H4]folate dehydrogenase (D) and methenyl[H4]folate cyclohydrolase (C). These activities often coexist as part of a multifunctional enzyme and there are several lines of evidence suggesting that their substrates bind at overlapping sites. Little is known, however, about the nature of this site or the identity of the active-site residues for this enzyme family. RESULTS: We have determined, to 1.5 A resolution, the structure of a dimer of the D/C domain of the human trifunctional cytosolic enzyme with bound NADP cofactor, using the MAD technique. The D/C subunit is composed of two alpha/beta domains that assemble to form a wide cleft. The cleft walls are lined with highly conserved residues and NADP is bound along one wall. The NADP-binding domain has a Rossmann fold, characterized by a modified diphosphate-binding loop fingerprint-GXSXXXG. Dimerization occurs by antiparallel interaction of two NADP-binding domains. Superposition of the two subunits indicates domain motion occurs about a well-defined hinge region. CONCLUSIONS: Analysis of the structure suggests strongly that folate-binding sites for both activities are within the cleft, providing direct support for the proposed overlapping site model. The orientation of the nicotinamide ring suggests that in the dehydrogenase-catalyzed reaction hydride transfer occurs to the pro-R side of the ring. The identity of the cyclohydrolase active site is not obvious. We propose that a conserved motif-Tyr52-X-X-X-Lys56- and/or a Ser49-Gln100-Pro102 triplet have a role in this activity. The 3-D structure of a folate-dependent dehydrogenase/cyclohydrolase bifunctional enzyme at 1.5 A resolution.,Allaire M, Li Y, MacKenzie RE, Cygler M Structure. 1998 Feb 15;6(2):173-82. PMID:9519408[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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