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Updated: Aug 8, 2026

Targeting Cysteine Thiols for in Vitro Site-specific Glycosylation of Recombinant Proteins
Published on: October 4, 2017
Sequential protection-modification method for selective sulfhydryl group derivatization in proteins having more than
1Department of Molecular and Cellular Biology, University of California, Berkeley 94720.
This study generalizes a method to introduce non-natural amino acids into proteins, enabling precise protein modification even with multiple cysteine residues present. This technique is crucial for advancing protein engineering and drug development.
Area of Science:
- Biochemistry
- Protein Engineering
- Synthetic Biology
Background:
- Site-specific incorporation of non-natural amino acids is vital for protein engineering.
- Previous methods were limited to proteins with a single, genetically introduced cysteine residue.
Purpose of the Study:
- To generalize a method for site-specific protein modification using a non-natural lysine analog.
- To enable the introduction of S-(2-aminoethyl)cysteine into proteins with endogenous cysteine residues.
Main Methods:
- Alkylation of cysteine residues with 2-bromoethylamine.
- Protection of active site cysteine via bound cofactor.
- Reversible derivatization of non-active site cysteines.
- Partial protein unfolding using urea to expose target cysteines for alkylation.
Main Results:
- Successfully generalized the alkylation method to proteins with multiple endogenous cysteines.
- Demonstrated site-specific incorporation of S-(2-aminoethyl)cysteine in aspartate aminotransferase.
- Maintained enzyme activity after modification through cofactor protection and refolding.
Conclusions:
- The generalized method allows for precise protein engineering in complex protein environments.
- This technique expands the toolkit for creating novel proteins with tailored functions.
- Potential applications in drug development and biochemical research.
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