Methionine 129 Variant of Human Prion Protein Oligomerizes More Rapidly than the Valine 129 Variant

• Published in: The Journal of biological chemistry 2004-07, Vol.279 (30), p.31390-31397
• Main Authors: Tahiri-Alaoui, Abdessamad, Gill, Andrew C., Disterer, Petra, James, William
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M401754200

The human PrP gene ( PRNP ) has two common alleles that encode either methionine or valine at codon 129. This polymorphism modulates disease susceptibility and phenotype of human transmissible spongiform encyphalopathies, but the molecular mechanism by which these effects are mediated remains unclear. Here, we compared the misfolding pathway that leads to the formation of β-sheet-rich oligomeric isoforms of the methionine 129 variant of PrP to that of the valine 129 variant. We provide evidence for differences in the folding behavior between the two variants at the early stages of oligomer formation. We show that Met 129 has a higher propensity to form β-sheet-rich oligomers, whereas Val 129 has a higher tendency to fold into α-helical-rich monomers. An equimolar mixture of both variants displayed an intermidate folding behavior. We show that the oligomers of both variants are initially a mixture of α- and β-rich conformers that evolve with time to an increasingly homogeneous β-rich form. This maturation process, which involves no further change in proteinase K resistance, occurs more rapidly in the Met 129 form than the Val 129 form. Although the involvement of such β-rich oligomers in prion pathogenesis is speculative, the misfolding behavior could, in part, explain the higher susceptibility of individuals that are methionine homozygote to both sporadic and variant Creutzfeldt-Jakob disease.