Intestinal fatty acid binding proteins: Importance of alpha I-helix in fatty acid mechanism to phospholipids membranes.

GISELA FRANCHINI, BETINA CÓRSICO, HORACIO GARDA Y JUDITH STORCH.

Bariloche, provincia de Rio Negro.

Congreso; XXXII Reunión Anual de la Sociedad Argentina de Biofísica.; 2003

Sociedad Argentina de Biofísica

Intestinal fatty acid binding protein (I-FABP) and liver FABP (L-FABP) are both coexpressed in intestinal entherocytes. These proteins have a well conserved terciary structure consisting of a b-barrel domain with a hydrophobic pocket and a portal domain with two short a-helixes (aI y aII). Fatty acid transfer from I-FABP to membranes occurs by direct collisional interaction with lipid bilayer while L-FABP shows an aqueous diffusion mediated process. In addition we have shown the importance of the portal region in determining the FA transfer mechanism to artificial membranes. Considering the existence of an amphipatic helix (aI) in I-FABP, we decided to construct two chimeric proteins by exchanging the aI region between I and L-FABP.  We obtained a chimeric protein with the b barrel of L-FABP and the aI-helix of IFABP (aII-bLFABP) and the corresponding reversal chimeric (aIL-bIFABP). Integrity of the binding cavity assays (Kd and Kp determination) showed no drastic changes. A fluorescence resonance energy transfer assay was used to monitor the rate of transfer of FA to phospholipid membranes. Results showed important modifications in rate of transfer for aIL-bIFABP chimeric protein compared to wild-type I-FABP and no drastic change for aII-bLFABP chimera compared to wild-type LFABP.