PSMC5 also known as SUG1, TRIP1 is a multicatalytic proteinase complex with a highly ordered structure composed of 2 complexes, a 20S core and a 19S regulator. PSMC5 plays a crucial role as an ATPase subunit within the 26S proteasome complex, which is essential for the regulated degradation of ubiquitinated proteins. PSMC5 is localized in both the cytoplasm and nucleus, where PSMC5 is part of the 19S regulatory particle that confers substrate specificity and facilitates the ATP-dependent degradation of proteins, particularly those misfolded or damaged in the endoplasmic reticulum. PSMC5′s importance extends to involvement in the assembly of the 26S proteasome, which has been shown to be dependent on phosphorylation by specific protein kinases.