biostudies-literatureHangasky JANational Institute of General Medical SciencesNIGMS NIH HHS5750-8https://www.ebi.ac.uk/biostudies/studies/S-EPMC4165446biostudies-literatureUnknown53(36)Nonheme Fe(II)/αKG-dependent oxygenases catalyze diverse reactions, typically inserting an O atom from O2 into a C-H bond. Although the key to their catalytic cycle is the fact that binding and positioning of primary substrate precede O2 activation, the means by which substrate binding stimulates turnover is not well understood. Factor Inhibiting HIF (FIH) is a Fe(II)/αKG-dependent oxygenase that acts as a cellular oxygen sensor in humans by hydroxylating the target residue Asn(803), found in the C-terminal transactivation domain (CTAD) of hypoxia inducible factor-1. FIH-Gln(239) makes two hydrogen bonds with CTAD-Asn(803), positioning this target residue over the Fe(II). We hypothesized the positioning of the side chain of CTAD-Asn(803) by FIH-Gln(239) was critical for stimulating O2 actiBiochemistrySubstrate positioning by Gln(239) stimulates turnover in factor inhibiting HIF, an αKG-dependent hydroxylase.PMC4165446R01-GM0774313T32-GM008515R01-GM077413T32 GM008515Knapp MJHangasky JAIvison GTfalseSubstrate positioning by Gln(239) stimulates turnover in factor inhibiting HIF, an αKG-dependent hydroxylase.Nonheme Fe(II)/αKG-dependent oxygenases catalyze diverse reactions, typically inserting an O atom from O2 into a C-H bond. Although the key to their catalytic cycle is the fact that binding and positioning of primary substrate precede O2 activation, the means by which substrate binding stimulates turnover is not well understood. Factor Inhibiting HIF (FIH) is a Fe(II)/αKG-dependent oxygenase that acts as a cellular oxygen sensor in humans by hydroxylating the target residue Asn(803), found in the C-terminal transactivation domain (CTAD) of hypoxia inducible factor-1. FIH-Gln(239) makes two hydrogen bonds with CTAD-Asn(803), positioning this target residue over the Fe(II). We hypothesized the positioning of the side chain of CTAD-Asn(803) by FIH-Gln(239) was critical for stimulating O2 acti2014-01-01T00:00:00Z2014 Sep2026-05-04T05:19:13.462Z2026-04-07T20:07:03.646ZS-EPMC41654462511966310.1021/bi500703s