Abstract
The ubiquitin-activating enzyme E1 catalyzes the first step in ubiquitin conjugation. We have cloned and sequenced the cDNA for human E1. This clone predicts a protein of 110,450 Da. Cys-194 lies within a region of identity to active-site Cys-88 of the ubiquitin carrier protein E2, suggesting a potential role for this region in enzymatic function of this protein. In addition, Cys-454 lies within a region of identity to the thiol ester consensus sequence of several proteins involved in thioester formation. Tissue distribution reveals a single 3.5-kilobase E1 message ubiquitous among tissues and cell lines.