A comparative study of the conformational properties of Escherichia coli-derived rat intestinal and liver fatty acid binding proteins.
Fourier transform infrared spectroscopy has been used to examine the conformation in aqueous solution of Escherichia coli-expressed rat intestinal and liver fatty-acid binding proteins (I-FABP and L-FABP, respectively). While I-FABP is known from X-ray analysis to have a predominantly beta-structure with 10 antiparallel beta-strands forming two orthogonal sheets that surround the ligand binding pocket, no structural data are available for L-FABP. As expected for homologous proteins with related functions, the secondary structures of I-FABP and L-FABP are very similar. In both proteins, the conformation-sensitive amide-I band shows the maximum absorption at around 1630 cm-1, proving that beta-sheet is the major structural element. However, there are three critical differences between I-FABP and L-FABP; (i), a different solvent accessibility of the protein backbone; (ii), a different pH sensitivity and (iii), a different thermostability, with L-FABP being thermally more stable than I-FABP. These results suggest that, in spite of having a similar overall conformation, the architecture of these proteins is stabilized by slightly different interactions. Such dissimilarities, well-paralleled by fatty-acid binding studies, may provide a structural basis for their functional diversification.
Muga
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National Research Council of Canada, Institute for Biodiagnostics, Winnipeg, Manitoba.
Cistola
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Mantsch
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D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics; D003001:Cloning, Molecular; D004926:Escherichia coli; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007422:Intestines / Q000737:chemistry*; D008099:Liver / Q000737:chemistry*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D013055:Spectrophotometry, Infrared; D013696:Temperature
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; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011994:Recombinant Proteins