title: Assessing the role of aromatic residues in the amyloid aggregation of human muscle acylphosphatase.
abstract: Among the many parameters that have been proposed to promote amyloid fibril formation is the pi-stacking of aromatic residues. We have studied the amyloid aggregation of several mutants of human muscle acylphosphatase in which an aromatic residue was substituted with a non-aromatic one. The aggregation rate was determined using the Thioflavin T test under conditions in which the variants populated initially an ensemble of partially unfolded conformations. Substitutions in aggregation-promoting fragments of the sequence result in a dramatically decreased aggregation rate of the protein, confirming the propensity of aromatic residues to promote this process. Nevertheless, a statistical analysis shows that the measured decrease of aggregation rate following mutation arises predominantly from a reduction of hydrophobicity and intrinsic beta-sheet propensity. This suggests that aromatic residues favor aggregation because of these factors rather than for their aromaticity.
authors.affiliation: Dipartimento di Scienze Biochimiche, Università degli Studi di Firenze, 50134, Firenze, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bemporad
authors.forename: Niccolò
authors.initials: N
authors.lastname: Taddei
authors.forename: Massimo
authors.initials: M
authors.lastname: Stefani
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Chiti
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism*; D052160:Benzothiazoles; D001718:Birefringence; D002942:Circular Dichroism; D003224:Congo Red / Q000737:chemistry / Q000378:metabolism; D003627:Data Interpretation, Statistical; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D009132:Muscles / Q000378:metabolism*; D044367:Phase Transition; D010649:Phenylalanine / Q000737:chemistry; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013844:Thiazoles / Q000737:chemistry / Q000378:metabolism; D014270:Trifluoroethanol / Q000378:metabolism / Q000494:pharmacology; D014443:Tyrosine / Q000737:chemistry; D000097024:Acylphosphatase
chemical_list: D017766:Acid Anhydride Hydrolases; D000682:Amyloid; D052160:Benzothiazoles; D003224:Congo Red; D010649:Phenylalanine; D013844:Thiazoles; D014270:Trifluoroethanol; D014443:Tyrosine; D000097024:Acylphosphatase; C009462:thioflavin T