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Human Dihydrofolate Reductase Structural Data with Active Site Mutant Enzyme Complexes
Structural highlights
DiseaseDYR_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] FunctionDYR_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] 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 PubMedTo understand the role of specific active site residues in conferring selective dihydrofolate reductase (DHFR) inhibition from pathogenic organisms such as Pneumocystis carinii (pc) or Pneumocystis jirovecii (pj), the causative agent in AIDS pneumonia, it is necessary to evaluate the role of these residues in the human enzyme. We report the first kinetic parameters for DHFR from pjDHFR and pcDHFR with methotrexate (MTX), trimethoprim (TMP), and its potent analogue, PY957. We also report the mutagenesis and kinetic analysis of active site mutant proteins at positions 35 and 64 of human (h) DHFR and the crystal structure determinations of hDHFR ternary complexes of NADPH and PY957 with the wild-type DHFR enzyme, the single mutant protein, Gln35Lys, and two double mutant proteins, Gln35Ser/Asn64Ser and Gln35Ser/Asn64Phe. These substitutions place into human DHFR amino acids found at those sites in the opportunistic pathogens pcDHFR (Q35K/N64F) and pjDHFR (Q35S/N64S). The K(i) inhibition constant for PY957 showed greatest potency of the compound for the N64F single mutant protein (5.2 nM), followed by wild-type pcDHFR (K(i) 22 nM) and then wild-type hDHFR enzyme (K(i) 230 nM). Structural data reveal significant conformational changes in the binding interactions of PY957 in the hDHFR Q35S/N64F mutant protein complex compared to the other hDHFR mutant protein complexes and the pcDHFR ternary complex. The conformation of PY957 in the wild-type DHFR is similar to that observed for the single mutant protein. These data support the hypothesis that the enhanced selectivity of PY957 for pcDHFR is in part due to the contributions at positions 37 and 69 (pcDHFR numbering). This insight will help in the design of more selective inhibitors that target these opportunistic pathogens. Correlations of Inhibitor Kinetics for Pneumocystis jirovecii and Human Dihydrofolate Reductase with Structural Data for Human Active Site Mutant Enzyme Complexes (dagger) (double dagger).,Cody V, Pace J, Makin J, Piraino J, Queener SF, Rosowsky A Biochemistry. 2009 Feb 5. PMID:19196009[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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