Off-pathway aggregation can inhibit fibrillation at high protein concentrations

TY - JOUR

T1 - Off-pathway aggregation can inhibit fibrillation at high protein concentrations

AU - Deva, Taru

AU - Lorenzen, Nikolai

AU - Vad, Brian S

AU - Petersen, Steen V

AU - Thørgersen, Ida

AU - Enghild, Jan J

AU - Kristensen, Torsten

AU - Otzen, Daniel

N1 - Copyright © 2013. Published by Elsevier B.V.

PY - 2013/3

Y1 - 2013/3

N2 - Ribosomal protein S6 fibrillates readily at slightly elevated temperatures and acidic pH. We find that S6 fibrillation is retarded rather than favored when the protein concentration is increased above a threshold concentration of around 3.5mg/mL. We name this threshold concentration C(FR), the concentration at which fibrillation is retarded. Our data are consistent with a model in which this inhibition is due to the formation of an off-pathway oligomeric species with native-like secondary structure. The oligomeric species dominates at high protein concentrations but exists in dynamic equilibrium with the monomer so that seeding with fibrils can overrule oligomer formation and favors fibrillation under C(FR) conditions. Thus, fibrillation competes with formation of off-pathway oligomers, probably due to a monomeric conversion step that is required to commit the protein to the fibrillation pathway. The S6 oligomer is resistant to pepsin digestion. We also report that S6 forms different types of fibrils dependent on protein concentration. Our observations highlight the multitude of conformational states available to proteins under destabilizing conditions.

AB - Ribosomal protein S6 fibrillates readily at slightly elevated temperatures and acidic pH. We find that S6 fibrillation is retarded rather than favored when the protein concentration is increased above a threshold concentration of around 3.5mg/mL. We name this threshold concentration C(FR), the concentration at which fibrillation is retarded. Our data are consistent with a model in which this inhibition is due to the formation of an off-pathway oligomeric species with native-like secondary structure. The oligomeric species dominates at high protein concentrations but exists in dynamic equilibrium with the monomer so that seeding with fibrils can overrule oligomer formation and favors fibrillation under C(FR) conditions. Thus, fibrillation competes with formation of off-pathway oligomers, probably due to a monomeric conversion step that is required to commit the protein to the fibrillation pathway. The S6 oligomer is resistant to pepsin digestion. We also report that S6 forms different types of fibrils dependent on protein concentration. Our observations highlight the multitude of conformational states available to proteins under destabilizing conditions.

KW - Amyloid formation;

KW - s6

KW - Soluble oligomers

KW - Proteolysis

KW - Fibril morphology

KW - Acid cleavage

U2 - 10.1016/j.bbapap.2012.12.020

DO - 10.1016/j.bbapap.2012.12.020

M3 - Journal article

C2 - 23313095

SN - 0304-4165

VL - 1834

SP - 677

EP - 687

JO - BBA General Subjects

JF - BBA General Subjects

IS - 3

ER -