Context‐Dependence of the Reactivity of Cysteine and Lysine Residues
Name
ChemBioChem - 2022 - Boll - Context‐Dependence of the Reactivity of Cysteine and Lysine Residues.pdf
Description
Published version
Size
5.48 MB
Format
Adobe PDF
Checksum (MD5)
770d21fa7e164e8e93bde439b5a079ed
Author(s)
Boll, Linus B
Raines, Ronald T
Date Issued
July 19, 2022
Journal
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
Abstract
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.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
Terms of Use
Creative Commons Attribution-NonCommercial-NoDerivs License
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1002/cbic.202200258
