Oxidation of Dueling Cysteine Promotes Subunit Exchange in SOD1

Ao Yun Zhang; Chad M Dashnaw; Mayte Gonzalez; Jordan C Koone; Nick A Wells; Colin A Smith; Matthew J Guberman-Pfeffer; Bryan F Shaw

doi:10.1021/acschemneuro.3c00174

Oxidation of Dueling Cysteine Promotes Subunit Exchange in SOD1

ACS Chem Neurosci. 2023 Apr 6. doi: 10.1021/acschemneuro.3c00174. Online ahead of print.

Authors

Ao Yun Zhang¹, Chad M Dashnaw¹, Mayte Gonzalez¹, Jordan C Koone¹, Nick A Wells², Colin A Smith², Matthew J Guberman-Pfeffer¹, Bryan F Shaw¹

Affiliations

¹ Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76706, United States.
² Department of Chemistry, Wesleyan University, Middletown, Connecticut 06459, United States.

PMID: 37023050
DOI: 10.1021/acschemneuro.3c00174

Abstract

The heterodimerization of wild-type (WT) Cu, Zn superoxide dismutase-1 (SOD1) and mutant SOD1 might be a critical step in the pathogenesis of SOD1-linked amyotrophic lateral sclerosis (ALS). Post-translational modifications that accelerate SOD1 heterodimerization remain unidentified. Here, we used capillary electrophoresis to quantify the effect of cysteine-111 oxidation on the rate and free energy of ALS mutant/WT SOD1 heterodimerization. The oxidation of Cys₁₁₁-β-SH to sulfinic and sulfonic acid (by hydrogen peroxide) increased rates of heterodimerization (with unoxidized protein) by ∼3-fold. Cysteine oxidation drove the equilibrium free energy of SOD1 heterodimerization by up to ΔΔG = -5.11 ± 0.36 kJ mol^-1. Molecular dynamics simulations suggested that this enhanced heterodimerization, between oxidized homodimers and unoxidized homodimers, was promoted by electrostatic repulsion between the two "dueling" Cys₁₁₁-SO₂^-/SO₃^-, which point toward one another in the homodimeric state. Together, these results suggest that oxidation of Cys-111 promotes subunit exchange between oxidized homodimers and unoxidized homodimers, regardless of whether they are mutant or WT dimers.

Keywords: amyloid; capillary electrophoresis; motor neuron; oxidative stress; protein aggregation; reactive oxygen species; sulfenic; sulfinic; sulfonic acid.