The integrity of the alpha-helical domain of intestinal fatty acid binding protein is essential for the collision-mediated transfer of fatty acids to phospholipid membranes.

FRANCHINI GR; STORCH J; CÓRSICO B

BIOCHIMICA ET BIOPHYSICA ACTA (ENZIMOLOGY)

Año: 2007 vol. 1781 p. 192 - 199

0006-3002

Intestinal FABP (IFABP) and liver FABP (LFABP), homologous proteins expressed at high levels in intestinal absorptive cells, employ markedly different mechanisms of fatty acid transfer to acceptor model membranes. Transfer from IFABP occurs during protein-membrane-collisional interactions, while for LFABP transfer occurs by diffusion through the aqueous phase. In addition, transfer from IFABP is markedly faster than from LFABP. The overall goal of this study was to further explore the structural differences between IFABP and LFABP which underlie their large functional differences in ligand transport. In particular, we addressed the role of the aI-helix domain in the unique transport properties of intestinal FABP. A chimeric protein was engineered with the ‘body’ (ligand binding domain) of IFABP and the aI-helix of LFABP (a(I)LbIFABP), and the fatty acid transfer properties of the chimeric FABP were examined using a fluorescence resonance energy transfer assay.  The results showed a significant decrease in the absolute rate of FA transfer from a(I)LbIFABP compared to IFABP. The results indicate that the aI-helix is crucial for IFABP collisional FA transfer, and further indicate the participation of the aII-helix in the formation of a protein-membrane “collisional complex”. Photo-crosslinking experiments with a photoactivable reagent demonstrated the direct interaction of IFABP with membranes and further supports the importance of the aI helix of IFABP in its physical interaction with membranes.