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Systematic Tuning of Heme Redox Potentials and Its Effects on O(2) Reduction Rates in a Designed Oxidase in Myoglobin

[Image: see text] Cytochrome c Oxidase (CcO) is known to catalyze the reduction of O(2) to H(2)O efficiently with a much lower overpotential than most other O(2) reduction catalysts. However, methods by which the enzyme fine-tunes the reduction potential (E°) of its active site and the corresponding...

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Autores principales: Bhagi-Damodaran, Ambika, Petrik, Igor D., Marshall, Nicholas M., Robinson, Howard, Lu, Yi
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2014
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4151708/
https://www.ncbi.nlm.nih.gov/pubmed/25076049
http://dx.doi.org/10.1021/ja5054863
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author Bhagi-Damodaran, Ambika
Petrik, Igor D.
Marshall, Nicholas M.
Robinson, Howard
Lu, Yi
author_facet Bhagi-Damodaran, Ambika
Petrik, Igor D.
Marshall, Nicholas M.
Robinson, Howard
Lu, Yi
author_sort Bhagi-Damodaran, Ambika
collection PubMed
description [Image: see text] Cytochrome c Oxidase (CcO) is known to catalyze the reduction of O(2) to H(2)O efficiently with a much lower overpotential than most other O(2) reduction catalysts. However, methods by which the enzyme fine-tunes the reduction potential (E°) of its active site and the corresponding influence on the O(2) reduction activity are not well understood. In this work, we report systematic tuning of the heme E° in a functional model of CcO in myoglobin containing three histidines and one tyrosine in the distal pocket of heme. By removing hydrogen-bonding interactions between Ser92 and the proximal His ligand and a heme propionate, and increasing hydrophobicity of the heme pocket through Ser92Ala mutation, we have increased the heme E° from 95 ± 2 to 123 ± 3 mV. Additionally, replacing the native heme b in the CcO mimic with heme a analogs, diacetyl, monoformyl, and diformyl hemes, that posses electron-withdrawing groups, resulted in higher E° values of 175 ± 5, 210 ± 6, and 320 ± 10 mV, respectively. Furthermore, O(2) consumption studies on these CcO mimics revealed a strong enhancement in O(2) reduction rates with increasing heme E°. Such methods of tuning the heme E° through a combination of secondary sphere mutations and heme substitutions can be applied to tune E° of other heme proteins, allowing for comprehensive investigations of the relationship between E° and enzymatic activity.
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spelling pubmed-41517082015-07-30 Systematic Tuning of Heme Redox Potentials and Its Effects on O(2) Reduction Rates in a Designed Oxidase in Myoglobin Bhagi-Damodaran, Ambika Petrik, Igor D. Marshall, Nicholas M. Robinson, Howard Lu, Yi J Am Chem Soc [Image: see text] Cytochrome c Oxidase (CcO) is known to catalyze the reduction of O(2) to H(2)O efficiently with a much lower overpotential than most other O(2) reduction catalysts. However, methods by which the enzyme fine-tunes the reduction potential (E°) of its active site and the corresponding influence on the O(2) reduction activity are not well understood. In this work, we report systematic tuning of the heme E° in a functional model of CcO in myoglobin containing three histidines and one tyrosine in the distal pocket of heme. By removing hydrogen-bonding interactions between Ser92 and the proximal His ligand and a heme propionate, and increasing hydrophobicity of the heme pocket through Ser92Ala mutation, we have increased the heme E° from 95 ± 2 to 123 ± 3 mV. Additionally, replacing the native heme b in the CcO mimic with heme a analogs, diacetyl, monoformyl, and diformyl hemes, that posses electron-withdrawing groups, resulted in higher E° values of 175 ± 5, 210 ± 6, and 320 ± 10 mV, respectively. Furthermore, O(2) consumption studies on these CcO mimics revealed a strong enhancement in O(2) reduction rates with increasing heme E°. Such methods of tuning the heme E° through a combination of secondary sphere mutations and heme substitutions can be applied to tune E° of other heme proteins, allowing for comprehensive investigations of the relationship between E° and enzymatic activity. American Chemical Society 2014-07-30 2014-08-27 /pmc/articles/PMC4151708/ /pubmed/25076049 http://dx.doi.org/10.1021/ja5054863 Text en Copyright © 2014 American Chemical Society Terms of Use (http://pubs.acs.org/page/policy/authorchoice_termsofuse.html)
spellingShingle Bhagi-Damodaran, Ambika
Petrik, Igor D.
Marshall, Nicholas M.
Robinson, Howard
Lu, Yi
Systematic Tuning of Heme Redox Potentials and Its Effects on O(2) Reduction Rates in a Designed Oxidase in Myoglobin
title Systematic Tuning of Heme Redox Potentials and Its Effects on O(2) Reduction Rates in a Designed Oxidase in Myoglobin
title_full Systematic Tuning of Heme Redox Potentials and Its Effects on O(2) Reduction Rates in a Designed Oxidase in Myoglobin
title_fullStr Systematic Tuning of Heme Redox Potentials and Its Effects on O(2) Reduction Rates in a Designed Oxidase in Myoglobin
title_full_unstemmed Systematic Tuning of Heme Redox Potentials and Its Effects on O(2) Reduction Rates in a Designed Oxidase in Myoglobin
title_short Systematic Tuning of Heme Redox Potentials and Its Effects on O(2) Reduction Rates in a Designed Oxidase in Myoglobin
title_sort systematic tuning of heme redox potentials and its effects on o(2) reduction rates in a designed oxidase in myoglobin
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4151708/
https://www.ncbi.nlm.nih.gov/pubmed/25076049
http://dx.doi.org/10.1021/ja5054863
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