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

Deacon, OM and Karsisiotis, AI and Moreno-Chicano, T and Hough, MA and Macdonald, C and Blumenschein, TMA and Wilson, MT and Moore, GR and Worrall, JAR (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
Subjects: Q Science > QD Chemistry
Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health > Life Sciences, School of
Depositing User: Elements
Date Deposited: 21 Nov 2017 14:05
Last Modified: 10 Sep 2019 11:15
URI: http://repository.essex.ac.uk/id/eprint/20669

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