Influence of Electrostatic Interactions on the Fibrillation Process of Human Serum Albumin

Abstract

The fibrillation propensity of the multidomain protein human serum albumin (HSA) has been analyzed under physiological and acidic conditions at room and elevated temperatures with varying ionic strengths by different spectroscopic techniques. The kinetics of fibril formation under the different solution conditions and the structures of resulting fibrillar aggregates were also determined. In this way, we have observed that fibril formation is largely affected by electrostatic shielding: at physiological pH, fibrillation is progressively more efficient and faster in the presence of up to 50 mM NaCl; meanwhile, at larger salt concentrations, excessive shielding and further enhancement of the solution hydrophobicity might involve a change in the energy landscape of the aggregation process, which makes the fibrillation process difficult. In contrast, under acidic conditions, a continuous progressive enhancement of HSA fibrillation is observed as the electrolyte concentration in solution increases. Both the distinct ionization and initial structural states of the protein before incubation may be the origin of this behavior. CD, FT-IR, and tryptophan fluorescence spectra seem to confirm this picture by monitoring the structural changes in both protein tertiary and secondary structures along the fibrillation process. On the other hand, the fibrillation of HSA does not show a lag phase except at pH 3.0 in the absence of added salt. Finally, differences in the structure of the intermediates and resulting fibrils under the different conditions are also elucidated by TEM and FT-IR.

A comparative analysis of the folding and misfolding pathways of the third PDZ domain of PSD95 investigated under different pH conditions

“…At neutral pH this process is energetically favoured by the stable precursory intermediate state that already oligomerizes during heating from room temperature to 60 ºC [4]. A similar pH-dependent behavior has been observed in humanserum albumin fibrillation processes [23].…”

“…The relevant role of electrostatic interactions in the organization of amyloid fibrils has been described elsewhere [21][22][23]. Variations in pH can modulate the electrostatic balance between intra-and inter-molecular forces among protein molecules.…”

Improvement of heat-induced fibril assembly of soy β-conglycinin (7S Globulins) at pH 2.0 through electrostatic screening

“…Besides, their work also verified that fibril assembly rate of β-LG was slower at lower ionic strengths, which was initially stated by Aymard et al (1999). The impact of ionic strength on fibril assembly is different among distinct proteins, such as human serum albumin (Juárez, López, Cambón, Taboada, & Mosquera, 2009) and kidney bean protein isolate (rich in 7S globulins; Zhang et al, 2010).…”

Ions and the Protein Surface Revisited: Extensive Molecular Dynamics Simulations and Analysis of Protein Structures in Alkali-Chloride Solutions

“…Two pivotal examples were the activation and inhibition of pyruvate kinase by different alkali metal ions, 8 and the binding of F − to proteins, suggested to participate in its prophylactic action in dental caries. 9 Some of the more recent studies concentrated on protein-salt interactions during amyloid aggregation, 10 protein folding 11 and protein-protein recognition. 12 Many efforts have been devoted to the adaptation of experimental methods to account for binding of ions by various proteins.…”