Abstract
Selective modification of native proteins in live cells is one of the central challenges in recent chemical biology. As a unique bioorthogonal approach, ligand-directed chemistry recently emerged, but the slow kinetics limits its scope. Here we successfully overcome this obstacle using N-acyl-N-alkyl sulfonamide as a reactive group. Quantitative kinetic analyses reveal that ligand-directed N-acyl-N-alkyl sulfonamide chemistry allows for rapid modification of a lysine residue proximal to the ligand binding site of a target protein, with a rate constant of ~104 M−1 s−1, comparable to the fastest bioorthogonal chemistry. Despite some off-target reactions, this method can selectively label both intracellular and membrane-bound endogenous proteins. Moreover, the unique reactivity of N-acyl-N-alkyl sulfonamide enables the rational design of a lysine-targeted covalent inhibitor that shows durable suppression of the activity of Hsp90 in cancer cells. This work provides possibilities to extend the covalent inhibition approach that is currently being reassessed in drug discovery.
Highlights
Selective modification of native proteins in live cells is one of the central challenges in recent chemical biology
Given that our LD reagents have been shown to react with several canonical amino acids (e.g. Lys, His, Ser, Tyr and Glu) other than Cys[12,13,15,18], our efforts to develop a variety of LD chemistry may substantially contribute to extending chemical warheads that can be used for TCIs28
While the LD chemistries reported by our group (LDT, LDAI and LDBB) have proved to be applicable to selective protein labelling both in vitro and in living cells, they still suffer from sluggish reaction rates, requiring hours to a day to achieve acceptable levels of labelled products[14,15,18,19]
Summary
Selective modification of native proteins in live cells is one of the central challenges in recent chemical biology. Most bioorthogonal protein modification strategies typically require two steps: (i) the incorporation of a bioorthogonal reaction handle, such as a noncanonical amino acid or an enzyme domain or its substrate peptide, into a protein of interest (POI) using genetic engineering protocols, followed by (ii) a specific (bioorthogonal) reaction to attach a functional molecule, such as a drug, fluorophore, polymer or detection tag (Fig. 1a)[5] Powerful, this two-step method inevitably involves genetic manipulation, making it impossible to modify endogenous (i.e. naturally occurring) proteins in their native environments.
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