Protein-Labeling Reagents Selectively Activated by Copper(I)

Copper is an essential trace element
that participates in many
biological processes through its unique redox cycling between cuprous
(Cu+) and cupric (Cu2+) oxidation states. To
elucidate the biological functions of copper, chemical biology tools
that enable selective visualization and detection of copper ions and
proteins in copper-rich environments are required. Herein, we describe
the design of Cu+-responsive reagents based on a conditional
protein labeling strategy. Upon binding Cu+, the probes
generated quinone methide via oxidative bond cleavage, which allowed
covalent labeling of surrounding proteins with high Cu+ selectivity. Using gel- and imaging-based analyses, the best-performing
probe successfully detected changes in the concentration of labile
Cu+ in living cells. Moreover, conditional proteomics analysis
suggested intramitochondrial Cu+ accumulation in cells
undergoing cuproptosis. Our results highlight the power of Cu+-responsive protein labeling in providing insights into the
molecular mechanisms of Cu+ metabolism and homeostasis.