PSMA2

4R3O, 4R67, 5A0Q568319166ENSG00000106588ENSMUSG00000015671P25787P49722NM_002787NM_008944NP_002778NP_032970Proteasome subunit alpha type-2 is a protein that in humans is encoded by the PSMA2 gene. This protein is one of the 17 essential subunits (alpha subunits 1-7, constitutive beta subunits 1-7, and inducible subunits including beta1i, beta2i, beta5i) that contributes to the complete assembly of 20S proteasome complex.1iru: Crystal Structure of the mammalian 20S proteasome at 2.75 A resolution Proteasome subunit alpha type-2 is a protein that in humans is encoded by the PSMA2 gene. This protein is one of the 17 essential subunits (alpha subunits 1-7, constitutive beta subunits 1-7, and inducible subunits including beta1i, beta2i, beta5i) that contributes to the complete assembly of 20S proteasome complex. The gene PSMA2 encodes a member of the peptidase T1A family, that is a 20S core alpha subunit. Using FISH, the human gene HC3 (old nomenclature for PMSA2, 4.3kb with 3 exons) was mapped at chromosome band 6q27. The human protein proteasome subunit alpha type-2 is also known as 20S proteasome subunit alpha-2 (based on systematic nomenclature). The protein is 25.9 kDa in size and composed of 234 amino acids. The calculated theoretical pI of this protein is 6.77. The proteasome is a multicatalytic proteinase complex with a highly ordered 20S core structure. This barrel-shaped core structure is composed of 4 axially stacked rings of 28 non-identical subunits: the two end rings are each formed by 7 alpha subunits, and the two central rings are each formed by 7 beta subunits. Three beta subunits (beta1, beta2, and beta5) each contains a proteolytic active site and has distinct substrate preferences. Proteasomes are distributed throughout eukaryotic cells at a high concentration and cleave peptides in an ATP/ubiquitin-dependent process in a non-lysosomal pathway. Crystal structures of isolated 20S proteasome complex demonstrate that the two rings of beta subunits form a proteolytic chamber and maintain all their active sites of proteolysis within the chamber. Concomitantly, the rings of alpha subunits form the entrance for substrates entering the proteolytic chamber. In an inactivated 20S proteasome complex, the gate into the internal proteolytic chamber are guarded by the N-terminal tails of specific alpha-subunit. The proteolytic capacity of 20S core particle (CP) can be activated when CP associates with one or two regulatory particles (RP) on one or both side of alpha rings. These regulatory particles include 19S proteasome complexes, 11S proteasome complex, etc. Following the CP-RP association, the confirmation of certain alpha subunits will change and consequently cause the opening of substrate entrance gate. Besides RPs, the 20S proteasomes can also be effectively activated by other mild chemical treatments, such as exposure to low levels of sodium dodecylsulfate (SDS) or NP-14. The eukaryotic proteasome recognized degradable proteins, including damaged proteins for protein quality control purpose or key regulatory protein components for dynamic biological precesses. An essential function of a modified proteasome, the immunoproteasome, is the processing of class I MHC peptides. As a component of alpha ring, Proteasome subunit alpha type-2 contributes to the formation of heptameric alpha rings and substrate entrance gate. Importantly, alpha2 subunit plays an critical role in the assembly of 19S base and 20S. In a study using Saccharomyces cerevisiae proteasome core particle 20S and regulatory particle 19S (similar to human proteasome) base component to delineate the binding process between 19S and 20S, evidences showed that one 19S subunit, Rpt6, can insert its tail into the pocket formed by alpha2 and alpha3 subunit, facilitating the complex formation between 20S and 19S base component.