Context‐Dependence of the Reactivity of Cysteine and Lysine Residues
Author(s)
Boll, Linus B; Raines, Ronald T
DownloadPublished version (5.479Mb)
Publisher with Creative Commons License
Publisher with Creative Commons License
Creative Commons Attribution
Terms of use
Metadata
Show full item recordAbstract
The S-alkylation of Cys residues with a maleimide and the Nϵ -acylation of Lys residues with an N-hydroxysuccinimide (NHS) ester are common methods for bioconjugation. Using Cys and Lys derivatives as proxies, we assessed differences in reactivity depending on the position of Cys or Lys in a protein sequence. We find that Cys position is exploitable to improve site-selectivity in maleimide-based modifications. Reactivity decreases substantially in the order N-terminal>in-chain>C-terminal Cys due to modulation of sulfhydryl pKa by the α-ammonium and carboxylate groups at the termini. A lower pKa value yields a larger fraction thiolate, which promotes selectivity while somewhat decreasing thiolate nucleophilicity in accord with β n u c =0.41. Lowering pH and salt concentration enhances selectivity still further. In contrast, differences in the reactivity of Lys towards an NHS ester were modest due to an appreciable decrease in amino group nucleophilicity with a lower pKa of its conjugate acid. Hence, site-selective Lys modification protocols will require electrophiles other than NHS esters.
Date issued
2022-07-19Department
Massachusetts Institute of Technology. Department of ChemistryJournal
ChemBioChem
Publisher
Wiley
Citation
Boll, Linus B and Raines, Ronald T. 2022. "Context‐Dependence of the Reactivity of Cysteine and Lysine Residues." ChemBioChem, 23 (14).
Version: Final published version