ubiquitin activating enzyme complex https://github.com/geneontology/go-ontology/issues/14921 cellular_component A protein complex responsible for the catalysis of the reaction: E1 + ubiquitin + ATP--> E1-ubiquitin + AMP + PPi, where the E1-ubiquitin linkage is a thioester bond between the C-terminal glycine of Ub and a sulfhydryl side group of an E1 cysteine residue. This is the first step in a cascade of reactions in which ubiquitin is ultimately added to a protein substrate. GO:0120123 E1 ubiquitin-activating enzyme krc 2018-01-29T19:28:56Z E1 complex intracellular protein-containing complex catalytic complex