Kaneko K, Peretz D, Pan K M, Blochberger T C, Wille H, Gabizon R, Griffith O H, Cohen F E, Baldwin M A, Prusiner S B
Department of Neurology, University of California, San Francisco 94143, USA.
Proc Natl Acad Sci U S A. 1995 Nov 21;92(24):11160-4. doi: 10.1073/pnas.92.24.11160.
Conversion of the cellular isoform of prion protein (PrPC) into the scrapie isoform (PrPSc) involves an increase in the beta-sheet content, diminished solubility, and resistance to proteolytic digestion. Transgenetic studies argue that PrPC and PrPSc form a complex during PrPSc formation; thus, synthetic PrP peptides, which mimic the conformational pluralism of PrP, were mixed with PrPC to determine whether its properties were altered. Peptides encompassing two alpha-helical domains of PrP when mixed with PrPC produced a complex that displayed many properties of PrPSc. The PrPC-peptide complex formed fibrous aggregates and up to 65% of complexed PrPC sedimented at 100,000 x g for 1 h, whereas PrPC alone did not. These complexes were resistant to proteolytic digestion and displayed a high beta-sheet content. Unexpectedly, the peptide in a beta-sheet conformation did not form the complex, whereas the random coil did. Addition of 2% Sarkosyl disrupted the complex and rendered PrPC sensitive to protease digestion. While the pathogenic A117V mutation increased the efficacy of complex formation, anti-PrP monoclonal antibody prevented interaction between PrPC and peptides. Our findings in concert with transgenetic investigations argue that PrPC interacts with PrPSc through a domain that contains the first two putative alpha-helices. Whether PrPC-peptide complexes possess prion infectivity as determined by bioassays remains to be established.
朊病毒蛋白的细胞异构体（PrPC）转变为瘙痒病异构体（PrPSc）涉及β-折叠含量增加、溶解度降低以及对蛋白水解消化的抗性增强。转基因研究表明，在PrPSc形成过程中PrPC和PrPSc形成了复合物；因此，将模拟PrP构象多元性的合成PrP肽与PrPC混合，以确定其性质是否发生改变。包含PrP两个α-螺旋结构域的肽与PrPC混合时产生了一种复合物，该复合物表现出PrPSc的许多特性。PrPC-肽复合物形成了纤维状聚集体，高达65%的复合PrPC在100,000×g离心1小时后沉淀，而单独的PrPC则不会。这些复合物对蛋白水解消化具有抗性，并显示出高β-折叠含量。出乎意料的是，处于β-折叠构象的肽没有形成复合物，而无规卷曲构象的肽则形成了复合物。添加2%的十二烷基肌氨酸钠会破坏复合物，并使PrPC对蛋白酶消化敏感。虽然致病性A117V突变增加了复合物形成的效率，但抗PrP单克隆抗体可阻止PrPC与肽之间的相互作用。我们的研究结果与转基因研究一致，表明PrPC通过包含前两个假定α-螺旋的结构域与PrPSc相互作用。PrPC-肽复合物是否具有通过生物测定确定的朊病毒感染性仍有待确定。
