Despite being a low-abundance amino acid, cysteine plays an essential role in regulating protein function and serves as a satisfactory target of post-translational modifications and drug developments. To comprehensively assess reactive-cysteine-containing proteins, the development of chemical proteomic probes to label cysteine residues in human cells is an important objective. Cysteine modification using sulfonium-based probes is a novel method to identify reactive cysteine residues in proteins. Herein, we reported a set of "cysteine-reactive sulfonium-based (C-Sul)" probes to label the reactive cysteine sites in cellular proteins. Notably, water-soluble C-Sul probes have a significantly enhanced stability and cellular uptakes, displaying a high specificity toward reactive cysteines and compatibility with quantitative proteomic profiling. In comparison to the conventional iodoacetamide-based probe, C-Sul particularly has no inhibitory effects on cell viability, enabling its application in proteomic profiling of reactive cysteine residues under biorelevant conditions. We propose C-Sul probes as optimal tools of cysteine profiling for further broadly basic research.
Visible-light-mediated methods were heavily studied as a useful tool for cysteine-selective bio-conjugation; however, many current methods suffer from bio-incompatible reaction conditions and slow kinetics. To address these challenges, herein, we...
Disulfide-rich
architectures are valuable pharmacological tools
or therapeutics. Besides, a ligand-induced conjugate strategy offers
potential advantages in potency, selectivity, and duration of action
for novel covalent drugs. Combining the plentiful disulfide-rich architecture
library and ligand-induced conjugate via thiol–disulfide interchange
would supply great benefits for developing site specific covalent
inhibitors. Cysteine–cysteine (Cys–Cys) disulfide bonds
are intrinsically unstable in endogenous reductive environment, while
cysteine–penicillamine (Cys–Pen) disulfide bonds show
satisfactory stability. We envisioned the Cys–Pen disulfide
as a potential ligand-induced covalent bonding warhead, and this disulfide
could reconstruct with the protein cysteine in the vicinity of the
peptide binding site to form a new disulfide. To evaluate our design,
protein PLCγ1-c src homology 2 domain and RGS3-PDZ domain were
tested as models. Both proteins were successfully modified by Cys–Pen
disulfide and formed new disulfides between proteins and peptides.
The new disulfide was then analyzed to confirm it was a newly formed
disulfide bond between Pen of the ligand and a protein Cys near the
ligand binding site. HDAC4 was then chosen as a model by utilizing
its “CXXC” domain near its catalytic pocket. The designed
Cys–Pen cyclic peptide inhibitor of HDAC4 showed satisfactory
selectivity and inhibitory effect.
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