Cascio Paolo
Department of Veterinary Sciences, University of Turin, Grugliasco 10095, Italy.
Biomolecules. 2014 Jun 19;4(2):566-84. doi: 10.3390/biom4020566.
PA28αβ is a γ-interferon-induced 11S complex that associates with the ends of the 20S proteasome and stimulates in vitro breakdown of small peptide substrates, but not proteins or ubiquitin-conjugated proteins. In cells, PA28 also exists in larger complexes along with the 19S particle, which allows ATP-dependent degradation of proteins; although in vivo a large fraction of PA28 is present as PA28αβ-20S particles whose exact biological functions are largely unknown. Although several lines of evidence strongly indicate that PA28αβ plays a role in MHC class I antigen presentation, the exact molecular mechanisms of this activity are still poorly understood. Herein, we review current knowledge about the biochemical and biological properties of PA28αβ and discuss recent findings concerning its role in modifying the spectrum of proteasome's peptide products, which are important to better understand the molecular mechanisms and biological consequences of PA28αβ activity.
PA28αβ是一种γ干扰素诱导的11S复合物，它与20S蛋白酶体的末端结合，并刺激小肽底物在体外的分解，但不刺激蛋白质或泛素缀合蛋白的分解。在细胞中，PA28也与19S颗粒一起存在于更大的复合物中，这使得蛋白质能够进行ATP依赖的降解；尽管在体内，大部分PA28以PA28αβ-20S颗粒的形式存在，其确切的生物学功能在很大程度上尚不清楚。尽管有几条证据有力地表明PA28αβ在MHC I类抗原呈递中起作用，但其这一活性的确切分子机制仍知之甚少。在此，我们综述了目前关于PA28αβ生化和生物学特性的知识，并讨论了有关其在改变蛋白酶体肽产物谱方面作用的最新发现，这对于更好地理解PA28αβ活性的分子机制和生物学后果很重要。
