Human SUG1 (also known as p45, Rpt6, Cim3 and PSMC5) is a component of the 19S regulatory subunit of the 26S proteosome complex. It is one of the AAA ATPas found in the 19S regulatory complex that is thought to participate in the unfolding of ubiquitinated proteins in an ATP dependent manner. It has also been shown to directly interact with the nucleotide excision repair protein XPB.