NR APVI
AU Plakoutsi,G.; Taddei,N.; Stefani,M.; Chiti,F.
TI Aggregation of the acylphosphatase from S. solfataricus. The folded and partially unfolded states can be both precursors for amyloid formation.
QU The Journal of Biological Chemistry 2004 April 2; 279(14): 14111-14119
PT journal article
AB Protein aggregation is associated with a number of human pathologies including Alzheimer's and Creutzfeldt-Jakob diseases and the systemic amyloidoses. In this study, we used the acylphosphatase from the hyperthermophilic archeon S. solfataricus (Sso AcP) to investigate the mechanism of aggregation under conditions in which the protein maintains a folded structure. In the presence of 15-25% (v/v) trifluoroethanol, Sso AcP was found to form aggregates able to bind specific dyes such as thioflavine T, Congo red and ANS. The presence of aggregates was confirmed by circular dichroism and dynamic light scattering. Electron microscopy revealed the presence of small aggregates generally referred to as amyloid protofibrils. The monomeric form adopted by Sso AcP p rior to aggregation under these conditions retained enzymatic activity; in addition, folding was remarkably faster than unfolding. These observations indicate that Sso AcP adopts a folded, although possibly distorted, conformation prior to aggregation. Importantly, aggregation appeared to be 100-fold faster than unfolding under these conditions. Although aggregation of Sso AcP was faster at higher trifluoroethanol concentrations, in which the protein adopted a partially unfolded conformation, these findings suggest that the early events of amyloid fibril formation may involve an aggregation process consisting of the assembly of protein molecules in their folded state. This conclusion has a biological relevance as globular proteins normally spend most of their life time in folded structures.
AD Dipartimento di Scienze Biochimiche, Universit degli Studi di Firenze, Firenze, Firenze 50134.
SP englisch