Morillas M, Swietnicki W, Gambetti P, Surewicz W K
Department of Pathology, Case Western Reserve University, Cleveland, Ohio 44106, USA.
J Biol Chem. 1999 Dec 24;274(52):36859-65. doi: 10.1074/jbc.274.52.36859.
The prion protein (PrP) in a living cell is associated with cellular membranes. However, all previous biophysical studies with the recombinant prion protein have been performed in an aqueous solution. To determine the effect of a membrane environment on the conformational structure of PrP, we studied the interaction of the recombinant human prion protein with model lipid membranes. The protein was found to bind to acidic lipid-containing membrane vesicles. This interaction is pH-dependent and becomes particularly strong under acidic conditions. Spectroscopic data show that membrane binding of PrP results in a significant ordering of the N-terminal part of the molecule. The folded C-terminal domain, on the other hand, becomes destabilized upon binding to the membrane surface, especially at low pH. Overall, these results show that the conformational structure and stability of the recombinant human PrP in a membrane environment are substantially different from those of the free protein in solution. These observations have important implications for understanding the mechanism of the conversion between the normal (PrP(C)) and pathogenic (PrP(Sc)) forms of prion protein.
活细胞中的朊病毒蛋白（PrP）与细胞膜相关联。然而，此前所有关于重组朊病毒蛋白的生物物理研究都是在水溶液中进行的。为了确定膜环境对PrP构象结构的影响，我们研究了重组人朊病毒蛋白与模型脂质膜的相互作用。结果发现该蛋白能与含酸性脂质的膜囊泡结合。这种相互作用依赖于pH值，在酸性条件下尤为强烈。光谱数据表明，PrP与膜的结合导致分子N端部分显著有序排列。另一方面，折叠的C端结构域在与膜表面结合时会变得不稳定，尤其是在低pH值时。总体而言，这些结果表明，重组人PrP在膜环境中的构象结构和稳定性与溶液中的游离蛋白有很大不同。这些观察结果对于理解朊病毒蛋白正常（PrP(C)）和致病（PrP(Sc)）形式之间的转化机制具有重要意义。
