Description_x000D_ General description_x000D_ Among ubiquitin-conjugating enzymes, the mammalian ubiquitin conjugating enzyme UbcH1, is unique in its ability to catalyze the in vitro synthesis of unanchored Lys48-linked poly-ubiquitin chains from mono- or poly-ubiquitin, E1, and ATP. In addition, UbcH1 can catalyze the cyclization of longer poly-ubiquitin chains, including tetra- and penta-ubiquitin. Recombinant UbcH1 charges and supports ubiquitinylation in vitro. Typical enzyme concentration to support conjugation in vitro is 100 nM to 1 μM._x000D_ Physical form_x000D_ Supplied at a concentration of 1.0 mg/ml in 20 mM TBS, pH 7.5 containing 1.0 mM DTT.