D98D, A FUNTIONAL ALL-b-SHEET ABRIDGED FORM OF INTESTINAL FATTY ACID BINDING PROTEIN (IFABP)

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

Salta, Salta, Argentina

Congreso; 3rd Latin American Protein Society Meeting. XXXIX Annual Meeting of Argentinean Biophysical Society (SAB), Workshop CeBEM, structural Biology in Latin America.; 2010

Intestinal fatty acid binding protein (IFABP) is a 15 kDa intracellular lipid binding protein exhibiting a b-barrel fold that resembles a clamshell. The b-barrel, which encloses the ligand binding cavity, consists of two perpendicular five-stranded b-sheets with an intervening helix-turn-helix motif between strands A and B. Despite the fact that naturally occurring b-sheet proteins avoid edge-to-edge aggregation through a variety of strategies, the addition of a structure-promoting cosolvent such as 2,2,2-trifluoroethanol (TFE) can induce conformational changes that might trigger the onset of aggregation. With the aim of identifying the structural features involved in promoting or delaying aggregation, here we investigated the effects of 2,2,2-trifluoroethanol (TFE) on the structure and the propensity to aggregation of IFABP. The protein aggregates maximally in 25 % (v/v) TFE and, within the range of total protein concentration tested (9-35 mM), the underlying mechanism of aggregation seems to obey a relatively simple behabiour. In this sense, the gradual increase of the turbidity wavelength exponent reflects the temporal change of the distribution of oligo and polymeric species in favor of larger species. Moreover, Congo Red and thioflavin-T binding experiments suggest that the aggregates induced by TFE share amyloid-like properties, and transmission electron microscopy (TEM) data do not exclude their fibrillar morphology. In addition, a significant TFE concentration dependent effect on the overall protein conformation occurs as revealed by fluorescence and circular dichroism spectroscopies.