Protein Labeling & Modification
Proteins are made up of polypeptide chains, and their biological functions are largely determined by the correct folding, size, and the presence of reactive functional groups throughout the polypeptide chain. The ability to make site-specific protein modifications allows researchers to explore a wide array of protein properties and their biological functions. Technologies for protein labeling and modification include the addition of fluorophores, biotin, and other small molecules, which are used to study protein-protein interactions, protein folding, overall protein structure, and their biological roles in cellular processes,
Overview
Fluorescent Protein Labeling
The discovery and widespread use of green fluorescent protein (GFP) has revolutionized biological research. GFP and its derivatives are used to tag proteins, allowing for their detection and quantification in tissues and cells. This technology is especially useful for studying specific protein complexes in techniques such as ELISA and western blotting. However, the large size of GFP may disrupt the function of the tagged protein. To address this, smaller fluorescent tags, biotin, or non-natural amino acids with biorthogonal functionality are used to minimize the impact on protein function while still providing the benefits of fluorescence.
Enzyme-Protein Conjugation
Enzyme-protein conjugation is another method for labeling proteins. Common enzymes used for conjugation include alkaline phosphatase (AP) and horseradish peroxidase (HRP). This technique provides several advantages, including signal amplification and the versatility of various signal outputs such as fluorescence, chemiluminescence, or colorimetric detection. These outputs make enzyme-protein conjugation ideal for immunohistochemistry (IHC) or immunofluorescence (IF) applications, aiding in the detection of proteins in tissues and cells.
Emerging Protein Labeling Technologies
In disease research and drug discovery, targeted protein degradation technologies are gaining attention. Proteolysis-targeting chimeras (PROTACs) are bifunctional molecules that bind both to a target disease protein and to an E3 ligase, leading to the targeted degradation of the protein. This approach combines high specificity for disease-related proteins with the ability to harness the cell’s internal protein degradation mechanisms, making it a promising technology for identifying novel drug targets and developing therapeutics.