title: Critical nucleus size for disease-related polyglutamine aggregation is repeat-length dependent.
abstract: Because polyglutamine (polyQ) aggregate formation has been implicated as playing an important role in expanded CAG repeat diseases, it is important to understand the biophysics underlying the initiation of aggregation. Previously, we showed that relatively long polyQ peptides aggregate by nucleated growth polymerization and a monomeric critical nucleus. We show here that over a short range of repeat lengths, from Q(23) to Q(26), the size of the critical nucleus for aggregation increases from monomeric to dimeric to tetrameric. This variation in nucleus size suggests a common duplex antiparallel β-sheet framework for the nucleus, and it further supports the feasibility of an organized monomeric aggregation nucleus for longer polyQ repeat peptides. The data also suggest that a change in the size of aggregation nuclei may have a role in the pathogenicity of polyQ expansion in this series of familial neurodegenerative diseases.
authors.affiliation: Structural Biology Department, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: Karunakar
authors.initials: K
authors.lastname: Kar
authors.forename: Murali
authors.initials: M
authors.lastname: Jayaraman
authors.forename: Bankanidhi
authors.initials: B
authors.lastname: Sahoo
authors.forename: Ravindra
authors.initials: R
authors.lastname: Kodali
authors.forename: Ronald
authors.initials: R
authors.lastname: Wetzel
mesh_terms: D006801:Humans; D007700:Kinetics; D019636:Neurodegenerative Diseases / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D017433:Protein Structure, Secondary
chemical_list: D010455:Peptides; C097188:polyglutamine