Five enzymes of the Arg/N-degron pathway form a targeting complex: The concept of superchanneling

Significance The Arg/N-degron pathway targets proteins for degradation by recognizing their N-terminal residues. In the present study, we used in vivo and in vitro binding assays to identify specific multienzyme targeting complexes of the Arg/N-degron pathway in yeast (Saccharomyces cerevisiae ) and human cells. These targeting complexes contain N-terminal amidases, an arginyltransferase, and specific ubiquitin ligases of the Arg/N-degron pathway. Enzymes or assemblies of enzymes that catalyze sequential reactions have been observed to exhibit substrate channeling, in which a reaction intermediate can be transferred between active sites of interacting enzymes without release of intermediate to the bulk solution. It remains to be determined whether targeting complexes discovered in the present work function to enable substrate channeling.