Subunit Stoichiometry of Human Proteasomes

Abstract

Subunits from human placental proteasomes were separated by two-dimensional polyacrylamide gel electrophoresis. The amino acid composition of proteins from individual spots were determined. Some of the spots had identical amino acid compositions, confirming that they contain isoforms of the same subunit. Proteasomes from HeLa cells, labelled with 3Hleucine, were precipitated with an antibody and similarly separated into subunits. The radioactivity in each subunit was measured. The subunit stoichiometry was then calculated from these data and the leucine contents in the subunits. Each of the 14 major subunits of human proteasomes are apparently present in equal amounts.

Altered Composition of Liver Proteasome Assemblies Contributes to Enhanced Proteasome Activity in the Exceptionally Long-Lived Naked Mole-Rat

“…Levels of α7 were two-fold higher in naked mole-rat lysates when compared to mice whereas α4 and β4 were three and four-fold higher in lysates from the longer lived species (Figure 4 A, B). These diverse trends in changes of the total content of constitutive and catalytic proteasome subunits that should exist in relatively equal amounts [9], [44] can be explained by upstream upregulation of the genes responsible for those protein products or by a mixed population of proteasome assemblies. To test the latter hypothesis, the contents of two immunoproteasome catalytic subunits β5i and β2i were also measured.…”

Molecular aberrations in the MHC class I-restricted pathway for antigen presentation in methylcholanthrene sarcomas from nude mice: discrepancies between MHC mRNA and surface protein

“…The method used was that described by Hendil [41], with a few modifications. Briefly, 5 × 10 6 monolayer tumour cells were grown in 125 cm 2 tissue culture flasks (A/S Nunc) for 24 h with 15 ml Eagles' minimal essential medium supplemented with 5% FCS, 0 .…”

Intermediate-type 20 S Proteasomes in HeLa Cells: “Asymmetric” Subunit Composition, Diversity and Adaptation

“…[26][27][28] The subtype pattern of these proteasomes analysed by high-resolution anionexchange chromatography comprises three subtypes designated HLI, HLII and HLIII Figure 1(a). Figure 1.…”