Ubiquitin-like proteins fall into two classes: the first class, ubiquitin-like modifiers (UBLs) function as modifiers in a manner analogous to that of ubiquitin. Examples of UBLs are SUMO, Rub1 (also called Nedd8), Apg8 and Apg12. Proteins of the second class include parkin, RAD23 and DSK2, are designated ubiquitin-domain proteins (UDPs). These proteins contain domains that are related to ubiquitin but are otherwise unrelated to each other. In contrast to UBLs, UDPs are not conjugated to other proteins. In yeast, autophagy, the delivery of cytoplasmic components to the lysosome/vacuole for degradation, requires a ubiquitin-like protein conjugation system, in which Apg12 is covalently bound to Apg12-Apg5 and Apg16.
This purified antibody was prepared from rabbit serum after repeated immunizations with recombinant yeast APG12 protein.