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Crystal structure of human FIH D201E variant in complex with Zn, alpha-ketoglutarate, and HIF1 alpha peptide.Crystal structure of human FIH D201E variant in complex with Zn, alpha-ketoglutarate, and HIF1 alpha peptide.
Structural highlights
FunctionHIF1N_HUMAN Hydroxylates HIF-1 alpha at 'Asp-803' in the C-terminal transactivation domain (CAD). Functions as an oxygen sensor and, under normoxic conditions, the hydroxylation prevents interaction of HIF-1 with transcriptional coactivators including Cbp/p300-interacting transactivator. Involved in transcriptional repression through interaction with HIF1A, VHL and histone deacetylases. Hydroxylates specific Asn residues within ankyrin repeat domains (ARD) of NFKB1, NFKBIA, NOTCH1, ASB4, PPP1R12A and several other ARD-containing proteins. Also hydroxylates Asp and His residues within ARDs of ANK1 and TNKS2, respectively. Negatively regulates NOTCH1 activity, accelerating myogenic differentiation. Positively regulates ASB4 activity, promoting vascular differentiation.[1] [2] [3] [4] [5] [6] [7] [8] Publication Abstract from PubMedThe factor inhibiting hypoxia inducible factor-1alpha (FIH) is a nonheme Fe(II)/alphaKG oxygenase using a 2-His-1-Asp facial triad. FIH activates O2 via oxidative decarboxylation of alpha-ketoglutarate (alphaKG) to generate an enzyme-based oxidant which hydroxylates the Asn803 residue within the C-terminal transactivation domain (CTAD) of HIF-1alpha. Tight coupling of these two sequential reactions requires a structural linkage between the Fe(II) and the substrate binding site to ensure that O2 activation occurs after substrate binds. We tested the hypothesis that the facial triad carboxylate (Asp201) of FIH linked substrate binding and O2 binding sites. Asp201 variants of FIH were constructed and thoroughly characterized in vitro using steady-state kinetics, crystallography, autohydroxylation, and coupling measurements. Our studies revealed each variant activated O2 with a catalytic efficiency similar to that of wild-type (WT) FIH (kcataKM(O2)=0.17muM-1min-1), but led to defects in the coupling of O2 activation to substrate hydroxylation. Steady-state kinetics showed similar catalytic efficiencies for hydroxylation by WT-FIH (kcat/KM(CTAD)=0.42muM-1min-1) and D201G (kcat/KM(CTAD)=0.34muM-1min-1); hydroxylation by D201E was greatly impaired, while hydroxylation by D201A was undetectable. Analysis of the crystal structure of the D201E variant revealed steric crowding near the diffusible ligand site supporting a role for sterics from the facial triad carboxylate in the O2 binding order. Our data support a model in which the facial triad carboxylate Asp201 provides both steric and polar contacts to favor O2 access to the Fe(II) only after substrate binds, leading to coupled turnover in FIH and other alphaKG oxygenases. The facial triad in the alpha-ketoglutarate dependent oxygenase FIH: A role for sterics in linking substrate binding to O2 activation.,Hangasky JA, Taabazuing CY, Martin CB, Eron SJ, Knapp MJ J Inorg Biochem. 2016 Oct 17;166:26-33. doi: 10.1016/j.jinorgbio.2016.10.007. PMID:27815979[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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