Protein Labeling in Live Cells for Immunological Applications.

Protein labeling is often an important aspect of immunological experiments, as it allows observation of cellular processes, including protein synthesis and trafficking. Many protein labeling methods require permeabilization and fixation of cells, damaging the cells and preventing observation of processes in real time. However, a number of bioconjugation techniques allow protein labeling inside living cells to allow visualization of cellular processes as they occur and to facilitate retrieval of desired proteins. In this Topical Review, we describe bioconjugation methods that allow specific labeling of intracellular proteins of interest and discuss their applications to immunological studies. We focus on protein fusions, biotinylation, fluorescein arsenical helix binder (FlAsH) and resorufin arsenical helix binder (ReAsH) labeling, and tetrazine ligation.