NR AXRC
AU Leliveld,S.R.
TI Conformation, Self-Association and Ligand Binding Behaviour of The Expanded Octarepeat Domain of The Prion Protein
QU International Conference - Prion 2007 (26.-28.9.2007) Edinburgh International Conference Centre, Edinburgh, Scotland, UK - Book of Abstracts: Protein Misfolding P01.13
IA http://www.prion2007.com/pdf/Prion Book of Abstracts.pdf
PT Konferenz-Poster
AB Insertion of additional repeats into the PrP gene has been genetically linked to familial Creutzfeldt-Jakob disease (fCJD). Consequently, expansion of the N-terminal octarepeat (OR) domain from 4 (wild-type) up to 13 consecutive repeats appears to make PrPc prone to prion conversion. The OR domain itself is however redundant for the propagation of pre-existing infectivity and transgenic mice expressing mutant PrP with extra repeats develop neurological disease but no prion infectivity. Hence, we assumed that expanded OR domains can initiate the formation of new prions by capturing PrP molecules in such a way as to facilitate conversion or through the enhanced recruitment of host factors. Recently, we have shown that the expanded OR domain alone is a highly selective ligand for a subpopulation of PrPsc from infected hamster brain. In addition, we showed how the expanded but not the wild-type domains self-associate, forming well-defined multimeric complexes. Both features are strictly pH-dependent, occurring only at physiological pH. We then compared the conformation of the expanded to that of the wild-type OR domain. For this purpose, we expressed 4-, 8-, 10- and 13-OR fragments as N-terminal fusions to the protein G B1 domain (7 kDa), since the fragments alone are poorly soluble at pH >7. Using CD spectroscopy, we found that the conformation of the 13-OR fragment did not differ significantly from that of the wild-type version. Both fragments displayed a CD profile that suggests a polyproline helix II-like conformation, setting it apart from a nonstructured state. Furthermore, the self-association of the expanded OR domain was found to depend exclusively on hydrophobic interactions, showing a distinct dissociation threshold at 0.2% sarkosyl, as determined by dynamic light scattering. Thus, we present the first detailed characterization of the wild-type and mutant OR domain at physiological pH, showing it to have an extended but non-random conformation.
AD R. Leliveld, Research Centre Jülich, Institute for Neuroscience and Biophysics, Germany
SP englisch
PO Schottland
EA pdf-Datei und Poster (abweichender Titel: Probing the effect of octarepeat insertions on the conformation of the N- and C-terminal domains of the prion protein)