Precision Labeling of Native Antibodies with Lock Coupling

Area of Science:

• Biochemistry
• Chemical Biology
• Biotechnology

Background:

• Stable protein complexes are crucial for biotechnology but can dissociate, limiting applications.
• Existing methods for protein modification can be complex or lack precision.

Purpose of the Study:

• To introduce a simple, selective, one-step reaction for forming stable isopeptide bonds between proteins.
• To develop a method for precise labeling of native antibodies for advanced imaging and biomaterial applications.

Main Methods:

• Developed 'lock coupling,' a reaction between interfacial lysine and glutamate/aspartate side chains using EDC catalyst.
• Optimized reaction conditions (pH, reagent addition order) to minimize nonspecific cross-linking.
• Engineered GB1 protein for antibody Fc domain attachment and introduced cysteine for facile conjugation of probes (fluorophores, nanocrystals).

Main Results:

• Demonstrated successful formation of stable isopeptide bonds for precise native antibody labeling.
• Showcased uniform attachment of a defined number of probes to antibodies without extensive purification.
• Validated labeled antibodies in live-cell imaging, serving as a stable alternative to secondary antibodies for multicolor immunostaining.

Conclusions:

• Lock coupling offers a versatile and efficient method for protein modification and precise probe synthesis.
• This technique has broad potential for developing advanced protein-based probes for imaging, biomaterials, and medicine.
• The method leverages natural protein interactions and widespread amino acid pairings for robust bioconjugation.