Copper-zinc superoxide dismutase is activated through a sulfenic acid intermediate at a copper-ion entry site

Morgan M. Fetherolf; Stefanie D. Boyd; Alexander B. Taylor; Hee Jong Kim; James A. Wohlschlegel; Ninian J. Blackburn; P. John Hart; Dennis R. Winge; Duane D. Winkler

doi:10.1074/jbc.M117.775981

Copper-zinc superoxide dismutase is activated through a sulfenic acid intermediate at a copper-ion entry site

¹ University of Utah Health Sciences Center School of Medicine, United States;
² University of Texas at Dallas, United States;
³ University of Texas Health Science Center at San Antonio, United States;
⁴ University of California Los Angeles, United States;
⁵ Oregon Health and Science University, United States

↵* Corresponding author; email: duane.winkler{at}utdallas.edu

Author contributions: MMF, SDB, ABT, HJK and DDW conducted the research presented; MMF, NJB, DDW, PJH, JAW and DRW contributed to data analysis and interpretation, MMF, NJB, DDW, PJH and DRW drafted and edited the manuscript; and DDW, NJB, JAW and DRW contributed ideas for experimentation. All authors approved the final version of the manuscript.

Abstract

Metallo-chaperones are a diverse family of trafficking molecules that provide metal ions to protein targets for use as cofactors. The copper chaperone for Sod1 (Ccs1) activates immature copper-zinc superoxide dismutase (Sod1) by delivering copper and facilitating the oxidation of the Sod1 intramolecular disulfide bond. Here, we present structural, spectroscopic, and cell-based data supporting a novel copper-induced mechanism for Sod1 activation. Ccs1 binding exposes an electropositive cavity and proposed "entry site" for copper ion delivery on immature Sod1. Copper-mediated sulfenylation leads to a sulfenic acid intermediate that eventually resolves to form the Sod1 disulfide bond with concomitant release of copper into the Sod1 active site. Sod1 is the predominant disulfide bond requiring enzyme in the cytoplasm and this copper-induced mechanism of disulfide bond formation obviates the need for a thiol/disulfide oxidoreductase in that compartment.