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1a4i

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[[Image:1a4i.gif|left|200px]]
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{{STRUCTURE_1a4i| PDB=1a4i | SCENE= }}
{{STRUCTURE_1a4i| PDB=1a4i | SCENE= }}
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'''HUMAN TETRAHYDROFOLATE DEHYDROGENASE / CYCLOHYDROLASE'''
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===HUMAN TETRAHYDROFOLATE DEHYDROGENASE / CYCLOHYDROLASE===
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==Overview==
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BACKGROUND: 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.
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(as it appears on PubMed at http://www.pubmed.gov), where 9519408 is the PubMed ID number.
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{{ABSTRACT_PUBMED_9519408}}
==About this Structure==
==About this Structure==
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[[Category: Oxidoreductase]]
[[Category: Oxidoreductase]]
[[Category: Thf]]
[[Category: Thf]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 09:48:01 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 16:06:25 2008''

Revision as of 13:06, 30 June 2008

Image:1a4i.png

Template:STRUCTURE 1a4i

HUMAN TETRAHYDROFOLATE DEHYDROGENASE / CYCLOHYDROLASE

Template:ABSTRACT PUBMED 9519408

About this Structure

1A4I is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

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

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