3s7a
From Proteopedia
Human dihydrofolate reductase binary complex with PT684
Structural highlights
Disease[DYR_HUMAN] Defects in DHFR are the cause of megaloblastic anemia due to dihydrofolate reductase deficiency (DHFRD) [MIM:613839]. DHFRD is an inborn error of metabolism, characterized by megaloblastic anemia and/or pancytopenia, severe cerebral folate deficiency, and cerebral tetrahydrobiopterin deficiency. Clinical features include variable neurologic symptoms, ranging from severe developmental delay and generalized seizures in infancy, to childhood absence epilepsy with learning difficulties, to lack of symptoms.[1] [2] Function[DYR_HUMAN] Key enzyme in folate metabolism. Contributes to the de novo mitochondrial thymidylate biosynthesis pathway. Catalyzes an essential reaction for de novo glycine and purine synthesis, and for DNA precursor synthesis. Binds its own mRNA and that of DHFRL1.[3] [4] Publication Abstract from PubMedIn order to understand the structure-activity profile observed for a series of substituted dibenz[b,f]azepine antifolates, the crystal structure of the binary complex of human dihydrofolate reductase (hDHFR) with the potent and selective inhibitor 2,4-diamino-6-{2'-O-(3-carboxypropyl)oxydibenz[b,f]-azepin-5-yl}methylpter idine (PT684) was determined to 1.8 A resolution. These data revealed that the carboxylate side chain of PT684 occupies two alternate positions, neither of which interacts with the conserved Arg70 in the active-site pocket, which in turn hydrogen bonds to water. These observations are in contrast to those reported for the ternary complex of mouse DHFR (mDHFR) with NADPH [Cody et al. (2008), Acta Cryst. D64, 977-984], in which the 3-carboxypropyl side chain of PT684 was hydrolyzed to its hydroxyl derivative, PT684a. The crystallization conditions differed for the human and mouse DHFR crystals (100 mM K(2)HPO(4) pH 6.9, 30% ammonium sulfate for hDHFR; 15 mM Tris pH 8.3, 75 mM sodium cacodylate, PEG 4K for mDHFR). Additionally, the side chains of Phe31 and Gln35 in the hDHFR complex have a single conformation, whereas in the mDHFR complex they occupied two alternative conformations. These data show that the hDHFR complex has a decreased active-site volume compared with the mDHFR complex, as reflected in a relative shift of helix C (residues 59-64) of 1.2 A, and a shift of 1.5 A compared with the ternary complex of Pneumocystis carinii DHFR (pcDHFR) with the parent dibenz[b,f]azepine PT653. These data suggest that the greater inhibitory potency of PT684 against pcDHFR is consistent with the larger active-site volume of pcDHFR and the predicted interactions of the carboxylate side chain with Arg75. Structural analysis of human dihydrofolate reductase as a binary complex with the potent and selective inhibitor 2,4-diamino-6-{2'-O-(3-carboxypropyl)oxydibenz[b,f]-azepin-5-yl}methylpter idine reveals an unusual binding mode.,Cody V, Pace J, Nowak J Acta Crystallogr D Biol Crystallogr. 2011 Oct;67(Pt 10):875-80. Epub 2011, Sep 8. PMID:21931219[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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