Ligand Conformational Bias Drives Enantioselective Modification of a Surface-Exposed Lysine on Hsp90

J Am Chem Soc. 2020 Feb 19;142(7):3392-3400. doi: 10.1021/jacs.9b09684. Epub 2020 Feb 3.


Targeted covalent modification of surface-exposed lysines is challenging due to their low intrinsic reactivity and high prevalence throughout the proteome. Strategies for optimizing the rate of covalent bond formation by a reversibly bound inhibitor (kinact) typically involve increasing the reactivity of the electrophile, which increases the risk of off-target modification. Here, we employ an alternative approach for increasing kinact of a lysine-targeted covalent Hsp90 inhibitor, independent of the reversible binding affinity (Ki) or the intrinsic electrophilicity. Starting with a noncovalent ligand, we appended a chiral, conformationally constrained linker, which orients an arylsulfonyl fluoride to react rapidly and enantioselectively with Lys58 on the surface of Hsp90. Biochemical experiments and high-resolution crystal structures of covalent and noncovalent ligand/Hsp90 complexes provide mechanistic insights into the role of ligand conformation in the observed enantioselectivity. Finally, we demonstrate selective covalent targeting of cellular Hsp90, which results in a prolonged heat shock response despite concomitant degradation of the covalent ligand/Hsp90 complex. Our work highlights the potential of engineering ligand conformational constraints to dramatically accelerate covalent modification of a distal, poorly nucleophilic lysine on the surface of a protein target.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor
  • HSP90 Heat-Shock Proteins / antagonists & inhibitors*
  • HSP90 Heat-Shock Proteins / chemistry
  • Humans
  • Ligands
  • Lysine / chemistry*
  • Stereoisomerism
  • Sulfones / chemical synthesis
  • Sulfones / chemistry
  • Sulfones / pharmacology*


  • HSP90 Heat-Shock Proteins
  • Ligands
  • Sulfones
  • Lysine