Regulating protein stability and turnover is a key task in the cell. Besides lysosomes, ubiquitin‐mediated proteasomal degradation comprises the major proteolytic pathway in eukaryotes. Proteins destined for degradation by the proteasome are conjugated by a ‘tag’, a ubiquitin chain to a lysine, through an extensively regulated enzymatic cascade. The ubiquitylated proteins are subsequently targeted for degradation by the 26S proteasome, the major proteolytic machinery for ubiquitylated proteins in the cell. Ubiquitylation can be considered as another covalent post‐translational modification and signal, comparable to acetylation, glycosylation, methylation, and phosphorylation. However, ubiquitylation has multiple roles in addition to targeting proteins for degradation. Depending on the number of ubiquitin moieties and the linkages made, ubiquitin also plays an important role in DNA repair, protein sorting and virus budding. Unregulated degradation of proteins, or abnormally stable proteins, interfere with several regulatory pathways, and the ubiquitin‐proteasome pathway is affected in a number of diseases, such as neurodegenerative diseases, cellular atrophies and malignancies. Therefore, dissecting the ubiquitin‐proteasome pathway and identifying proteins involved in conjunction with the signals required for specific degradation of certain substrates, would help in developing novel therapeutic approaches to treat diseases where the ubiquitin‐proteasome pathway is impaired. [from: Roos‐Mattjus P. and Sistonen L. The ubiquitin‐proteasome pathway (2009) Annals of Medicine 36(4): 285-295]

The 26S proteasome is an essential component of the ubiquitin-proteolytic pathway in eukaryotic cells and is responsible for the degradation of most cellular proteins. It is composed of a 20S proteasome catalytic core and regulatory particles at either end. The subunits of the 20S proteasome are classified into two families, α and β. In eukaryotes, the 20S proteasome contains seven α-type subunits and seven β-type subunits. The fourteen subunits are arranged in four rings of seven and form an α7β7β7α7 structure. This antibody recognizes multiple subunits of the 20S proteasome from all organisms tested from yeast to human and is suitable for immunoelectron microscopy.

References:
1) Haraguchi, C. M., Mabuchi, T., Hirata, S., Shoda, T., Tokumoto, T., Hoshi, K., Yokota, S. 2007. Possible function of caudal nuclear pocket: degradation of nucleoproteins by ubiquitin-proteasome system in rat spermatids and human sperm. J Histochem Cytochem 55, 585-595. PubMed: 17312012
2) Ohsaki, Y., Cheng, J., Fujita, A., Tokumoto, T., Fujimoto, T. 2006. Cytoplasmic lipid droplets are sites of convergence of proteasomal and autophagic degradation of apolipoprotein B. Mol Biol Cell 17, 2674-2683. PubMed: 16597703
3) Tokumoto, M., Horiguchi, R., Nagahama, Y., Ishikawa, K., Tokumoto, T. 2000. Two proteins, a goldfish 20S proteasome subunit and the protein interacting with 26S proteasome, change in the meiotic cell cycle. Eur J Biochem 267, 97-103. PubMed: 10601855

Regulating protein stability and turnover is a key task in the cell. Besides lysosomes, ubiquitin‐mediated proteasomal degradation comprises the major proteolytic pathway in eukaryotes. Proteins destined for degradation by the proteasome are conjugated by a ‘tag’, a ubiquitin chain to a lysine, through an extensively regulated enzymatic cascade. The ubiquitylated proteins are subsequently targeted for degradation by the 26S proteasome, the major proteolytic machinery for ubiquitylated proteins in the cell. Ubiquitylation can be considered as another covalent post‐translational modification and signal, comparable to acetylation, glycosylation, methylation, and phosphorylation. However, ubiquitylation has multiple roles in addition to targeting proteins for degradation. Depending on the number of ubiquitin moieties and the linkages made, ubiquitin also plays an important role in DNA repair, protein sorting and virus budding. Unregulated degradation of proteins, or abnormally stable proteins, interfere with several regulatory pathways, and the ubiquitin‐proteasome pathway is affected in a number of diseases, such as neurodegenerative diseases, cellular atrophies and malignancies. Therefore, dissecting the ubiquitin‐proteasome pathway and identifying proteins involved in conjunction with the signals required for specific degradation of certain substrates, would help in developing novel therapeutic approaches to treat diseases where the ubiquitin‐proteasome pathway is impaired. [from: Roos‐Mattjus P. and Sistonen L. The ubiquitin‐proteasome pathway (2009) Annals of Medicine 36(4): 285-295]

The 26S proteasome is an essential component of the ubiquitin-proteolytic pathway in eukaryotic cells and is responsible for the degradation of most cellular proteins. It is composed of a 20S proteasome catalytic core and regulatory particles at either end. The subunits of the 20S proteasome are classified into two families, α and β. In eukaryotes, the 20S proteasome contains seven α-type subunits and seven β-type subunits. The fourteen subunits are arranged in four rings of seven and form an α7β7β7α7 structure. This antibody recognizes multiple subunits of the 20S proteasome from all organisms tested from yeast to human and is suitable for immunoelectron microscopy.

References:
1) Haraguchi, C. M., Mabuchi, T., Hirata, S., Shoda, T., Tokumoto, T., Hoshi, K., Yokota, S. 2007. Possible function of caudal nuclear pocket: degradation of nucleoproteins by ubiquitin-proteasome system in rat spermatids and human sperm. J Histochem Cytochem 55, 585-595. PubMed: 17312012
2) Ohsaki, Y., Cheng, J., Fujita, A., Tokumoto, T., Fujimoto, T. 2006. Cytoplasmic lipid droplets are sites of convergence of proteasomal and autophagic degradation of apolipoprotein B. Mol Biol Cell 17, 2674-2683. PubMed: 16597703
3) Tokumoto, M., Horiguchi, R., Nagahama, Y., Ishikawa, K., Tokumoto, T. 2000. Two proteins, a goldfish 20S proteasome subunit and the protein interacting with 26S proteasome, change in the meiotic cell cycle. Eur J Biochem 267, 97-103. PubMed: 10601855