monomerization of Cu, Zn superoxide
dismutase (SOD1) is an early step along pathways of
misfolding linked to amyotrophic lateral sclerosis (ALS).
Monomerization requires the reversal of two post-translational
modifications that are thermodynamically favorable: (i)
dissociation of active-site metal ions and (ii) reduction of
intramolecular disulfide bonds. This study found, using amide
hydrogen/deuterium (H/D) exchange, capillary electrophoresis,
and lysine-acetyl protein charge ladders, that ALS-linked A4V SOD1 rapidly monomerizes and partially unfolds in an
external electric field (of physiological strength), without loss of metal ions, exposure to disulfide-reducing agents, or Joule
heating. Voltage-induced monomerization was not observed for metal-free A4V SOD1, metal-free WT SOD1, or metal-loaded
WT SOD1. Computational modeling suggested a mechanism for this counterintuitive effect: subunit macrodipoles of dimeric
SOD1 are antiparallel and amplified 2-fold by metal coordination, which increases torque at the dimer interface as subunits rotate
to align with the electric field.
monomerization of Cu, Zn superoxidedismutase (SOD1) is an early step along pathways ofmisfolding linked to amyotrophic lateral sclerosis (ALS).Monomerization requires the reversal of two post-translationalmodifications that are thermodynamically favorable: (i)dissociation of active-site metal ions and (ii) reduction ofintramolecular disulfide bonds. This study found, using amidehydrogen/deuterium (H/D) exchange, capillary electrophoresis,and lysine-acetyl protein charge ladders, that ALS-linked A4V SOD1 rapidly monomerizes and partially unfolds in anexternal electric field (of physiological strength), without loss of metal ions, exposure to disulfide-reducing agents, or Jouleheating. Voltage-induced monomerization was not observed for metal-free A4V SOD1, metal-free WT SOD1, or metal-loadedWT SOD1. Computational modeling suggested a mechanism for this counterintuitive effect: subunit macrodipoles of dimericSOD1 are antiparallel and amplified 2-fold by metal coordination, which increases torque at the dimer interface as subunits rotateto align with the electric field.
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