Term Name:	protein tag activity
Synonyms:	covalent modifier, protein tag, protein tagging activity, ubiquitin, ubiquitin-like protein modifier
Definition:	A molecular function exhibited by a protein that is covalently attached (AKA tagged or conjugated) to another protein where it acts as a marker, recognized by the cellular apparatus to target the tagged protein for some cellular process such as modification, sequestration, transport or degradation.
Ontology:	GO: Molecular Function [GO:0031386]    QuickGO    AmiGO