title: PA28 subunits of the mouse proteasome: primary structures and chromosomal localization of the genes.
abstract: The 20S proteasome is a multi-subunit protease responsible for the production of peptides presented by major histocompatibility complex (MHC) class I molecules. Recent evidence indicates that an interferon-gamma (IFN-gamma)-inducible PA28 activator complex enhances the generation of class I binding peptides by altering the cleavage pattern of the proteasome. In the present study, we determined the primary structures of the mouse PA28 alpha- and beta-subunits. The deduced amino acid sequences of the alpha- and beta-subunits were 49% identical. We also determined the primary structure of the mouse PA28 gamma-subunit (Ki antigen), a protein of unknown function structurally related to the alpha- and beta-subunits. The amino acid sequence identity of the gamma-subunit to the alpha- and beta-subunits was 40% and 32%, respectively. Interspecific backcross mapping showed that the mouse genes coding for the alpha- and beta-subunits (designated Psme1 and Psme2, respectively) are tightly linked and map close to the Atp5g1 locus on chromosome 14. Thus, unlike the LMP2 and LMP7 subunits, the IFN-gamma-inducible subunits of PA28 are encoded outside the MHC. The gene coding for the gamma-subunit (designated Psme3) was mapped to the vicinity of the Brca1 locus on chromosome 11. A computer search of the DNA databases identified a gamma-subunit-like protein in ticks and Caenorhabditis elegans, the organisms with no adaptive immune system. It appears that the IFN-gamma-inducible alpha- and beta-subunits emerged by gene duplication from a gamma-subunit-like precursor.
authors.affiliation: Department of Biochemistry, Hokkaido University School of Medicine, Sapporo 060, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Kandil
authors.forename: K
authors.initials: K
authors.lastname: Kohda
authors.forename: T
authors.initials: T
authors.lastname: Ishibashi
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.forename: M
authors.initials: M
authors.lastname: Kasahara
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001324:Autoantigens; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D017173:Caenorhabditis elegans; D018797:Cell Cycle Proteins; D002874:Chromosome Mapping; D003546:Cysteine Endopeptidases / Q000235:genetics*; D018076:DNA, Complementary / Q000737:chemistry / Q000302:isolation & purification; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D009124:Muscle Proteins; D010802:Phylogeny; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000737:chemistry / Q000235:genetics*; D051381:Rats; D016415:Sequence Alignment; D013987:Ticks
chemical_list: D001324:Autoantigens; D018797:Cell Cycle Proteins; D018076:DNA, Complementary; C099558:Ki antigen; D009097:Multienzyme Complexes; D009124:Muscle Proteins; C085047:PSME1 protein, human; D011506:Proteins; C490050:Psme1 protein, rat; C490052:Psme2 protein, rat; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C486213:Psme1 protein, mouse; C486214:Psme2 protein, mouse