Polyene fatty acid interactions with recombinant intestinal and liver fatty acid-binding proteins. Spectroscopic studies.
Binding and proximity relationships of fatty acids with recombinant rat liver fatty acid-binding protein (L-FABP) and intestinal fatty acid-binding protein (I-FABP) were studied with absorption and fluorescence spectroscopy. Protein aromatic amino acids were examined in the absence and presence of bound fatty acid. Second derivative absorbance spectroscopy of the apo- and holoproteins suggested that fatty acid binding altered the conformation of L-FABP, but not of I-FABP. Fatty acid binding also blocked the accessibility of L-FABP tyrosine and I-FABP tryptophan to Stern-Volmer quenching by acrylamide, indicating that these amino acids were present in the fatty acid-binding pocket. Forster energy transfer from I-FABP tryptophan to bound cis-parinaric acid resulted in quenching of tryptophan lifetime and appearance of sensitized lifetime of bound cis-parinaric acid. The calculated donor-acceptor distances were 16.9 +/- 0.6 and 19.2 +/- 0.3 A for I-FABP and L-FABP, respectively. Absorbance spectral shifts and ratios of fluorescence excitation maxima indicated that the parinaric acid microenvironment in the fatty acid-binding site of I-FABP was much less polar than that of L-FABP. Parinaric acids displayed similar rotational correlation time and limiting anisotropy when bound to I-FABP and to L-FABP. These results are consistent with a close proximity of bound fatty acids to the tyrosine and tryptophan residues and with immobilization of the polyene fatty acids in the fatty acid-binding site(s) of L-FABP and I-FABP. The two proteins differ in that only L-FABP has two fatty acid-binding sites and appears to undergo significant conformational change upon fatty acid binding.
Nemecz
G
G
Department of Pharmacology and Cell Biophysics, University of Cincinnati Medical Center, Ohio 45267-0004.
Jefferson
J R
JR
Schroeder
F
F
D000178:Acrylamides / Q000737:chemistry; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated; D005456:Fluorescent Dyes; D007413:Intestinal Mucosa / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011487:Protein Conformation; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan / Q000737:chemistry
D000178:Acrylamides; D002352:Carrier Proteins; C493320:Fabp1 protein, mouse; C493321:Fabp1 protein, rat; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D005456:Fluorescent Dyes; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011994:Recombinant Proteins; D014364:Tryptophan; C013641:parinaric acid