Transglutaminase-Catalyzed Site-Specific Conjugation of Small-Molecule Probes to Proteins in Vitro and on the Surface of Living Cells

摘要

Compared to green fluorescent protein (GFP),non-genetically encoded probes,such as organic dyes and inorganic nanoparticles,offer the possibility of smaller probe sizes and access to a much wider array of functionality,from photocrosslinking and photo-regulation to imaging of cellular processes by nonoptical methods,such as electron microscopy,magnetic resonance imaging,and positron emission tomography.The major limitation to the use of these probes in cells,however,is the shortage of robust methods for targeting them to specific proteins of interest.Recently,many new methodologies for protein labeling in cells have been reported.Most of these use special peptide or protein handles,which are genetically fused to the target protein and recruit the probe of interest via a covalent or noncovalent interaction.There is great variation among these methods in terms of labeling specificity,speed,stability,tag size,toxicity,and versatility for probe structure and cell type,and no single method yet excels in all these respects.Thus new methods are still needed to facilitate the routine use of non-genetically encoded probes in the cellular context.