Approach to study the complex unfolding mechanism of a pdz domain

GABRIELA TORCHIO; MARTHA INES BURGOS; MARTÍN ARÁN; MARIANA GALLO; GERARDO D. FIDELIO; MAURICIO SICA

Carlos Paz

Congreso; XLII Reunión Annual de la Sociedad Argentina de Biofísic; 2013

Sociedad Argentina de Biofísica.

Many PDZ domains have been extensively studied from a biophysical pespective as they are important and ubiquitous modules of protein-protein interactions, with particular characteristics of folfind and binding. The PDZ domain of the β2 syntrophin protein (β2S PDZ), which is directly involved in the regulation of insulin secretion. . foldingstability and in terms of other reported PDZ domains share the consensus folding model with behave as Our previous results showed that β2S PDZ does not of the SG to the actin cytoskeleton. inmovilizationimmobilization. This interaction is responsible for the named ICA512a transmembrane protein of the insulin secretion granule (SG) ICA512, This protein is found in the cytoplasm of pancreatic beta-cells, where it binds via its PDZ domain We have shown that thermal unfolding curves are not as expected for a protein that follows a two state nor a three state model of folding. Moreover, the unfolding curves of β2S PDZ are more reminiscent of those of a protein that follows a downhill regime, or multiple state mechanism of folding. Here we present extra evidence that supports the hypothesis of a complex folding mechanisms for β2S PDZ. Differential scanning calorimetry (DSC) and RMN experiments discard tshowed that no oligomerization occurs during thermal unfolding, at least at concentrations up to 2 mg/ml. Some degree of aggregation is detected at high temperatures, but this aggregation only seems to eliminate a minor population of β2S PDZ, as a second and a third scan of DSC are