Rpn1

Rpn1, short for regulatory particle non-ATPase subunit 1, is a protein component of the 19S regulatory particle of the 26S proteasome in eukaryotic cells. It is a non-enzymatic subunit located in the base of the regulatory particle and is conserved from yeast to humans. As part of the 19S RP, Rpn1 works alongside other base subunits and the ATPase ring to facilitate substrate processing for degradation by the 20S core particle.

Rpn1 contributes to the assembly and stability of the regulatory particle. It acts as a docking platform that helps organize interactions among base subunits and can influence the recognition and handling of ubiquitin-tagged substrates. By supporting the structure of the base and coordinating with ubiquitin receptors and shuttle factors, Rpn1 aids in the steps of substrate binding, unfolding, and translocation into the proteolytic core.

Functionally, Rpn1 is involved in the proteasome’s ability to degrade misfolded or regulatory proteins marked for destruction. Proper function of Rpn1 is important for maintaining protein homeostasis, and alterations in its activity can impact overall proteasome performance and cellular protein turnover.

Genetically, RPN1 is essential for proteasome function in many eukaryotes; loss or depletion of Rpn1 impairs proteasome activity and can affect cell viability and growth. Its evolutionary conservation highlights a core role in cellular protein quality control. Overall, Rpn1 is a key structural and functional component of the 19S regulatory particle that supports regulated proteolysis in the ubiquitin–proteasome system.