Tag-probe labeling methods for live-cell imaging of membrane proteins.

Instead of using reconstituted proteoliposomes, in situ investigations of membrane proteins in living cell membranes are important because the heterogeneous and dynamic nature of biomembranes significantly affects their behavior. Protein-specific labeling is a key technique for the detection of a target protein by fluorescence measurements, particularly fluorescence microscopy. However, conventional genetic fusion with fluorescent proteins has several shortcomings. Post-translational labeling methods using a genetically encodable tag and synthetic probes targeting to the tag can overcome these limitations. This review summarizes emerging tag-probe techniques for labeling specific membrane proteins and their applications, including endocytotic internalization, partitioning to specific membrane domains, interprotein interactions, and conformational changes.