Heightened Dynamics of the Oxidized Y48H Variant of Human Cytochrome c Increases Its Peroxidatic Activity

Deacon, Oliver, Karsisiotis, Andreas Ioannis, Moreno-Chicano, Tadeo, Hough, Michael A., Macdonald, Colin, Blumenschein, Tharin M.A., Wilson, Michael T., Moore, Geoffrey R. and Worrall, Jonathan A.R. (2017) Heightened Dynamics of the Oxidized Y48H Variant of Human Cytochrome c Increases Its Peroxidatic Activity. Biochemistry, 56 (46). 6111–6124. ISSN 0006-2960

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Abstract

Proteins performing multiple biochemical functions are called “moonlighting proteins” or extreme multifunctional (EMF) proteins. Mitochondrial cytochrome c is an EMF protein that binds multiple partner proteins to act as a signaling molecule, transfers electrons in the respiratory chain, and acts as a peroxidase in apoptosis. Mutations in the cytochrome c gene lead to the disease thrombocytopenia, which is accompanied by enhanced apoptotic activity. The Y48H variant arises from one such mutation and is found in the 40–57 Ω-loop, the lowest-unfolding free energy substructure of the cytochrome c fold. A 1.36 Å resolution X-ray structure of the Y48H variant reveals minimal structural changes compared to the wild-type structure, with the axial Met80 ligand coordinated to the heme iron. Despite this, the intrinsic peroxidase activity is enhanced, implying that a pentacoordinate heme state is more prevalent in the Y48H variant, corroborated through determination of a Met80 “off rate” of >125 s–1 compared to a rate of ∼6 s–1 for the wild-type protein. Heteronuclear nuclear magnetic resonance measurements with the oxidized Y48H variant reveal heightened dynamics in the 40–57 Ω-loop and the Met80-containing 71–85 Ω-loop relative to the wild-type protein, illustrating communication between these substructures. Placed into context with the G41S cytochrome c variant, also implicated in thrombocytopenia, a dynamic picture associated with this disease relative to cytochrome c is emerging whereby increasing dynamics in substructures of the cytochrome c fold serve to facilitate an increased population of the peroxidatic pentacoordinate heme state in the following order: wild type < G41S < Y48H.

Item Type: Article
Faculty \ School: Faculty of Science
Faculty of Science > School of Chemistry
Depositing User: Pure Connector
Date Deposited: 02 Nov 2017 10:43
Last Modified: 19 Sep 2019 00:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/65336
DOI: 10.1021/acs.biochem.7b00890

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