26S protease regulatory subunit 6A, also known as 26S proteasome AAA-ATPase subunit Rpt5, is an enzyme that in humans is encoded by the PSMC3 gene. This protein is one of the 19 essential subunits of a complete assembled 19S proteasome complex Six 26S proteasome AAA-ATPase subunits (Rpt1, Rpt2, Rpt3, Rpt4, Rpt5 (this protein), and Rpt6) together with four non-ATPase subunits (Rpn1, Rpn2, Rpn10, and Rpn13) form the base sub complex of 19S regulatory particle for proteasome complex.