Prokaryotic ubiquitin-like protein

Prokaryotic ubiquitin-like protein (Pup) is a functional analog of ubiquitin found in the prokaryote Mycobacterium tuberculosis. Like ubiquitin, Pup serves to direct proteins to the proteasome for degradation in the Pup-proteasome system (PPS).

Source: Wikipedia — Prokaryotic ubiquitin-like protein (CC BY-SA 4.0)