Question

Explain why site specific protein labeling is important. Give one example in medical application.

Answer 1

Site-specific protein labeling is an important technique in protein chemistry and is used for diverse applications ranging from creating protein conjugates to protein immobilization. Enzymatic reactions, including protein prenylation, have been widely exploited as methods to accomplish site-specific labeling.

The most straightforward method for targeting a small molecule to a protein sequence is to use a binding. In this approach, the protein of interest is expressed fused to a protein tag that is capable of binding to a small-molecule ligand. It is highly specific thats why this method preferred over other methods for specificity. For example antibody tags fused to localization signal sequences to target various hapten–fluorophore conjugates to specific subcellular compartments in live cells. Appending various biophysical probes to these ligands is synthetically straightforward and does not reduce binding affinity for the protein targets. Labeling with these tags is highly specific, and the method is versatile because it can accommodate probes of many different structures.

An application of site specific protein labeling is ELISA assay.  In an ELISA, an antigen must be immobilized on a solid surface and then complexed with an antibody that is linked to an enzyme. Detection is accomplished by assessing the conjugated enzyme activity via incubation with a substrate to produce a measureable product. The most crucial element of the detection strategy is a highly specific antibody-antigen interaction.