Isopeptag

An isopeptag is a chemical tag, specifically a peptide sequence, designed to be recognized and bound by a specific enzyme, typically a transpeptidase. These tags are used in protein engineering and biotechnology to facilitate site-specific labeling, conjugation, or immobilization of proteins.

The fundamental principle involves genetically fusing the isopeptag to a protein of interest. Then, the protein-isopeptag fusion is incubated with the target enzyme and a 'payload' molecule that is also a substrate for the enzyme. The enzyme catalyzes a covalent bond formation between the isopeptag and the payload, thereby specifically attaching the payload to the protein of interest.

The advantage of using isopeptags is the highly specific and controlled manner in which the payload is attached. This offers advantages over traditional chemical conjugation methods that often result in heterogeneous labeling. Different isopeptags exist, each engineered to be recognized by a specific enzyme. The choice of isopeptag depends on the desired enzyme-substrate pair and the specific application.

Applications of isopeptags include protein purification, protein immobilization onto solid supports, antibody-drug conjugate (ADC) generation, bioconjugation, and the creation of biosensors. The technology enables researchers to precisely control the site and stoichiometry of modifications on proteins, which is crucial for understanding protein function and developing new biotechnological tools.