Comparative effect of structural promoting additives on the conformation of a β-barrel protein family.

PONCINO, M.; ANGELANI, C.R.; DELFINO J.M.; CURTO L.M.

Salto

Congreso; Latin American Crosstalk in Biophysics and Physiology; 2015

SAB - SBF.uy

Δ98Δ and Δ78Δ are two functional all-β sheet variants of IFABP (intestinal fatty acid binding protein). Albeit displaying increased conformational plasticity, these variants exhibit a native-like β-barrel topology and are able to support a cooperative folding behavior. We have recently evaluated the effect of TFE on this β-barrel protein family. Surprisingly, the CD spectra of Δ78Δ and Δ98Δ are gradually modified, becoming indistinguishable from that of IFABP at 10% TFE. In this condition, the near UV CD spectra of all three proteins remain native-like. This evidence points to the consolidation of the conformation of the abridged variants. With the aim of understanding the underlying facts behind the conformational changes observed, we addressed the task of evaluating the effect of several additives that are widely used to enhance folding and prevent aggregation. Thus, proteins were incubated in the presence of low concentrations of urea, guanidinium chloride, ethanol, sodium sulfate and trimethylamine N-oxide (TMAO) among others and their effect was evaluated by the changes in the far and near UV-CD spectra. Finally, temperature-induced denaturation was used to reveal their impact on stability.