Wille H, Baldwin M A, Cohen F E, DeArmond S J, Prusiner S B
Department of Neurology, University of California, San Francisco 94143, USA.
Ciba Found Symp. 1996;199:181-99; discussion 199-201.
The prion protein (PrP) undergoes a profound conformational change when the cellular isoform (PrPc) is converted into the scrapie form (PrPSc). Limited proteolysis of PrPSc produces PrP27-30 which readily polymerizes into amyloid. To study the structure of PrP amyloid, we employed organic solvents that perturb protein conformation. 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP), which promotes alpha-helix formation, modified the ultrastructure of rod-shaped PrP amyloids, producing flattened ribbons with a more regular substructure. As the concentration of HFIP was increased, the beta-sheet content and proteinase K resistance of PrP27-30 as well as prion infectivity diminished. HFIP reversibly decreased the binding of Congo red dye to the rods, whereas inactivation of prion infectivity was irreversible. In contrast to 10% HFIP, 1,1,1-trifluoro-2-propanol (TFIP) did not inactivate prion infectivity but, similarly to HFIP, TFIP did alter the morphology of the rods and abolished Congo red binding. Our studies separate prion infectivity from the amyloid properties of PrP27-30 and underscore the dependence of prion infectivity on PrPSc conformation. Our results also demonstrate that the specific beta-sheet-rich structures required for prion infectivity are different from those needed for amyloid formation.
当细胞型朊蛋白（PrPc）转变为瘙痒病型（PrPSc）时，朊蛋白（PrP）会发生深刻的构象变化。对PrPSc进行有限的蛋白酶解会产生PrP27-30，它很容易聚合成淀粉样蛋白。为了研究PrP淀粉样蛋白的结构，我们使用了能扰乱蛋白质构象的有机溶剂。1,1,1,3,3,3-六氟-2-丙醇（HFIP）可促进α-螺旋形成，它改变了棒状PrP淀粉样蛋白的超微结构，产生了具有更规则亚结构的扁平条带。随着HFIP浓度的增加，PrP27-30的β-折叠含量、对蛋白酶K的抗性以及朊病毒感染性均降低。HFIP可逆地减少刚果红染料与棒状物的结合，而朊病毒感染性的失活是不可逆的。与10%的HFIP不同，1,1,1-三氟-2-丙醇（TFIP）不会使朊病毒感染性失活，但与HFIP类似，TFIP确实改变了棒状物的形态并消除了刚果红结合。我们的研究将朊病毒感染性与PrP27-30的淀粉样特性区分开来，并强调了朊病毒感染性对PrPSc构象的依赖性。我们的结果还表明，朊病毒感染性所需的富含特定β-折叠的结构与淀粉样蛋白形成所需的结构不同。
