Neuropathogenesis Division, The Roslin Institute and Royal (Dick) School of Veterinary Studies, The Alexander Robertson Building, Easter Bush Veterinary Centre, Roslin, Midlothian EH25 9RG, UK.
Biochemistry. 2010 Feb 23;49(7):1448-59. doi: 10.1021/bi901855z.
Transmissible spongiform encephalopathies (TSEs) are associated with the accumulation of deposits of an abnormal form, PrP(Sc), of the host-encoded prion protein, PrP(C). Amino acid substitutions in PrP(C) have long been known to affect TSE disease outcome. In extreme cases in humans, various mutations appear to cause disease. In animals, polymorphisms are associated with variations in disease susceptibility and, in sheep, several polymorphisms have been identified that are known to affect susceptibility of carriers to disease. The mechanisms of polymorphism-mediated modulation of disease susceptibility remain elusive, and we have been studying the effect of various amino acid substitutions at PrP codon 164 (mouse numbering), in the beta2-alpha2 loop region of the prion protein, to attempt to decipher how polymorphisms may affect disease susceptibility. Combined in vitro approaches suggest that there exists a correlation between the ability of protein variants to convert to abnormal isoforms in seeded conversion assays versus the thermal stability of the protein variants, as judged by both thermal denaturation and an unseeded in vitro oligomerization assay. We have performed molecular dynamics simulations to give an indication of backbone conformational changes as a result of amino acid changes and found that alteration of a single residue in PrP can result in local changes in structure that may affect global conformation and stability. Our results are consistent with modulation of disease susceptibility through differential protein stability leading to enhanced generic misfolding of TSE resistance-associated protein variants.
传染性海绵状脑病（TSE）与宿主编码的朊病毒蛋白 PrP（C）的异常形式 PrP（Sc）的积累有关。长期以来，人们一直知道 PrP（C）中的氨基酸取代会影响 TSE 疾病的结果。在人类的极端情况下，各种突变似乎导致了疾病的发生。在动物中，多态性与疾病易感性的变化有关，在绵羊中，已经确定了几种多态性，这些多态性已知会影响携带者对疾病的易感性。多态性介导的疾病易感性调节机制仍然难以捉摸，我们一直在研究在朊病毒蛋白的β2-α2 环区域中，PrP 密码子 164 位（小鼠编号）的各种氨基酸取代对疾病易感性的影响，试图解释多态性如何影响疾病易感性。结合体外方法表明，在种子转化测定中，蛋白质变异体向异常异构体转化的能力与蛋白质变异体的热稳定性之间存在相关性，这可以通过热变性和无种子体外寡聚化测定来判断。我们进行了分子动力学模拟，以给出由于氨基酸变化导致的骨架构象变化的指示，并发现 PrP 中单个残基的改变可能导致结构的局部变化，从而可能影响全局构象和稳定性。我们的结果与通过差异蛋白稳定性调节疾病易感性一致，从而增强了 TSE 抗性相关蛋白变异体的普遍错误折叠。
