title: Folding and amyloid-fibril formation for a series of human stefins' chimeras: any correlation?
abstract: To study the influence of whole secondary structure elements to the process of folding and amyloid-fibril formation, chimeras of stefins have been prepared. GdnHCl denaturation curves and folding rates (chevron plots) have been analyzed based on a two-state mechanism. The order of stability is: stefin A > aAbbbb > bAbbbb > stefin B = aBaaaa > bBaaaa, where the make up of chimeric proteins is designated by small letters representing the source of individual strands (a for stefin A, b for stefin B) and a capital letter representing the source of the helix (A for stefin A and B for stefin B). Only the fast folding reactions were included in the analysis and it has been found that stefin B folds the fastest (657 s(-1)). Similarly, fast folders are the chimeric proteins aBaaaa and bBaaaa, both of which contain the alpha-helix of stefin B. Unfolding rates correlate very well with protein stability, with the slowest rate for the most stable protein, stefin A. Amyloid-fibril growth was measured for each protein by monitoring thioflavin T fluorescence and was visualized using electron microscopy. The propensity to form amyloid-fibrils is in the order: stefin B > bAbbbb > aAbbbb > bBaaaa > aBaaaa > stefin A. This order does not correlate with stability, or with the folding or unfolding rates. Instead, the propensity to fibrillize is related to selected parts of structure, such as the beta-sheet of stefin B, and can be predicted reasonably well by calculating the beta-strand propensity of the denatured states.
authors.affiliation: Department of Biochemistry and Molecular Biology, Jozef Stefan Institute, Ljubljana, Slovenia.
authors.forename: Manca
authors.initials: M
authors.lastname: Kenig
authors.forename: Sasa
authors.initials: S
authors.lastname: Jenko-Kokalj
authors.forename: Magda
authors.initials: M
authors.lastname: Tusek-Znidaric
authors.forename: Marusa
authors.initials: M
authors.lastname: Pompe-Novak
authors.forename: Gregor
authors.initials: G
authors.lastname: Guncar
authors.forename: Dusan
authors.initials: D
authors.lastname: Turk
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Waltho
authors.forename: Rosemarie A
authors.initials: RA
authors.lastname: Staniforth
authors.forename: Franc
authors.initials: F
authors.lastname: Avbelj
authors.forename: Eva
authors.initials: E
authors.lastname: Zerovnik
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055312:Cystatin A; D055313:Cystatin B; D015891:Cystatins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers; D019791:Guanidine; D006801:Humans; D008958:Models, Molecular; D050506:Mutant Chimeric Proteins / Q000737:chemistry* / Q000235:genetics; D016133:Polymerase Chain Reaction; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary
chemical_list: D000682:Amyloid; C524994:CSTB protein, human; D055312:Cystatin A; D015891:Cystatins; D017931:DNA Primers; D050506:Mutant Chimeric Proteins; D055313:Cystatin B; D019791:Guanidine