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Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity.

ABSTRACT: Protein design is a useful strategy to interrogate the protein structure-function relationship. We demonstrate using a highly modular 3-stranded coiled coil (TRI-peptide system) that a functional type?2 copper center exhibiting copper nitrite reductase (NiR) activity exhibits the highest homogeneous catalytic efficiency under aqueous conditions for the reduction of nitrite to NO and H2 O. Modification of the amino acids in the second coordination sphere of the copper center increases the nitrite reductase activity up to 75-fold compared to previously reported systems. We find also that steric bulk can be used to enforce a three-coordinate CuI in a site, which tends toward two-coordination with decreased steric bulk. This study demonstrates the importance of the second coordination sphere environment both for controlling metal-center ligation and enhancing the catalytic efficiency of metalloenzymes and their analogues.

SUBMITTER: Koebke KJ

PROVIDER: S-EPMC5869106 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity.

Koebke Karl J KJ Yu Fangting F Salerno Elvin E Van Stappen Casey C Tebo Alison G AG Penner-Hahn James E JE Pecoraro Vincent L VL

Angewandte Chemie (International ed. in English) 20180126 15

Protein design is a useful strategy to interrogate the protein structure-function relationship. We demonstrate using a highly modular 3-stranded coiled coil (TRI-peptide system) that a functional type 2 copper center exhibiting copper nitrite reductase (NiR) activity exhibits the highest homogeneous catalytic efficiency under aqueous conditions for the reduction of nitrite to NO and H<sub>2</sub> O. Modification of the amino acids in the second coordination sphere of the copper center increases ...[more]

PMID: 29316146

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Project description:The factor inhibiting HIF (FIH) is a proximate oxygen sensor for human cells, hydroxylating Asn(803) within the ?-subunit of the hypoxia inducible factor (HIF). FIH is an ?-ketoglutatrate (?KG)-dependent, non-heme Fe(II) dioxygenase, in which Fe(II) is coordinated by a (His(2)Asp) facial triad, ?KG, and H(2)O. Hydrogen bonding among the facial triad, the HIF-Asn(803) side chain, and various second-sphere residues suggests a functional role for the second coordination sphere in tuning the chemistry of the Fe(II) center. Point mutants of FIH were prepared to test the functional role of the ?KG-centered (Asn(205) and Asn(294)) or HIF-Asn(803)-centered (Arg(238) and Gln(239)) second-sphere residues. The second sphere was tested for local effects on priming Fe(II) to react with O(2), oxidative decarboxylation, and substrate positioning. Steady-sate kinetics were used to test for overall catalytic effects; autohydroxylation rates were used to test for priming and positioning, and electronic spectroscopy was used to assess the primary coordination sphere and the electrophilicity of ?KG. Asn(205) ? Ala and Asn(294) ? Ala mutants exhibited diminished rates of steady-state turnover, while minimally affecting autohydroxylation, consistent with impaired oxidative decarboxylation. Blue-shifted metal to ligand charge transfer transitions for (Fe+?KG)FIH indicated that these point mutations destabilized the ?* orbitals of ?KG, further supporting a slowed rate of oxidative decarboxylation. The Arg(238) ? Met mutant exhibited steady-state rates too low to measure and diminished product yields, suggesting impaired substrate positioning or priming; the Arg(238) ? Met mutant was capable of O(2) activation for the autohydroxylation reaction. The Gln(239) ? Asn mutant exhibited significantly slowed steady-state kinetics and diminished product yields, suggesting impaired substrate positioning or priming. As HIF binding to the Gln(239) ? Asn mutant stimulated autohydroxylation, it is more likely that this point mutant simply mispositions the HIF-Asn(803) side chain. This work combines kinetics and spectroscopy to show that these second-sphere hydrogen bonds play roles in promoting oxidative decarboxylation, priming Fe(II) to bind O(2), and positioning HIF-Asn(803).

Dataset Information

Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity.

Publications

Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity.

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