Protein Labelling

Protein labelling kits for site-specific biotinylation and streptavidin-based detection

Enzymatic biotinylation attaches a single biotin tag to antibodies or recombinant proteins at a defined site, without disrupting antigen-binding or catalytic activity, which suits your pull-down assays, SPR, and other streptavidin-based workflows. The reaction uses E. coli biotin ligase (BirA) to attach one biotin molecule to a 15-amino-acid AviTag sequence at a defined lysine, so every molecule you label carries exactly one biotin and gives you consistent streptavidin-binding stoichiometry across experiments. In vitro kits biotinylate your purified AviTag-fusion proteins directly, while companion E. coli expression strains support in vivo biotinylation during recombinant expression. This removes the post-purification enzyme incubation step from your high-throughput protein production.

Pick by activity preservation.

1. Indiscriminate. NHS-ester for amines. Over-labelling inactivates protein function. Aim for one to two labels per protein.
2. Cysteine-specific. Maleimide. Preserves more activity if cysteines are non-essential.
3. Site-specific. Sortase, SpyTag, or LplA enzymatic tags. Cleanest preserved activity.
4. Click-chemistry handles. For orthogonal labelling later.
5. Stoichiometry. For antibody-fluorophore conjugates labelling degree above 4-6 typically reduces antibody binding.

GeneCopoeia supplies protein-labelling reagent kits.