T-CrAsH: A heterologous chemical crosslinker

Copper-free click chemistry is currently the most promising and most rapidly developing technology for performing tailored chemical reactions inside intact living cells and animals. Its potential is particularly intensely explored in the field of live cell imaging, for both proteins and metabolites. Here we expand the application spectrum of click reactions to the chemical crosslinking of two proteins of choice in living cells. By combining strain-promoted Diels-Alder cycloaddition with FlAsH-based labeling of peptidic tetracysteine motifs, we developed the membrane-permeating reversible crosslinker T-CrAsH. We demonstrate the feasibility of the method both in vitro and inside cells. The biggest advantage of this new tool is the small size of the crosslinkable groups; this significantly decreases the risk of functional interference. Click meets FlAsH: Combination of two click chemistry and biarsenical derivatives led to the synthesis and first use of the membrane-permeating chemical crosslinker T-CrAsH. This tool is useful for specific and reversible crosslinking of two proteins in vitro and in living cells. T-CrAsH also has potential for the manipulation or detection of protein-metabolite and protein-DNA interactions.