Lipid specificity and location of the sterol carrier protein-2 fatty acid-binding site: a fluorescence displacement and energy transfer study.
Although it was recently recognized that sterol carrier protein-2 (SCP-2) interacts with fatty acids, little is known regarding the specificity of SCP-2 for long-chain fatty acids or branched-chain fatty-acid-like molecules. Likewise the location of the fatty-acid binding site within SCP-2 is unresolved. A fluorescent cis-parinaric acid displacement assay was used to show that SCP-2 optimally interacted with 14-22 carbon chain lipidic molecules: polyunsaturated fatty acids > monounsaturated, saturated > branched-chain isoprenoids > branched-chain phytol-derived fatty acids. In contrast, the other major fatty-acid binding protein in liver, fatty-acid binding protein (L-FABP), displayed a much narrower carbon chain preference in general: polyunsaturated fatty acids > branched-chain phytol-derived fatty acids > 14- and 16-carbon saturated > branched-chain isoprenoids. However, both SCP-2 and L-FABP displayed a very similar unsaturated fatty-acid specificity profile. The presence and location of the SCP-2 lipid binding site were investigated by fluorescence energy transfer. The distance between the SCP-2 Trp50 and bound cis-parinaric acid was determined to be 40 A. Thus, the SCP-2 fatty-acid binding site appeared to be located on the opposite side of the SCP-2 Trp50. These findings not only contribute to our understanding of the SCP-2 ligand binding site but also provide evidence suggesting a potential role for SCP-2 and/or L-FABP in metabolism of branched-chain fatty acids and isoprenoids.
Frolov
A
A
Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station 77843-4466, USA.
Miller
K
K
Billheimer
J T
JT
Cho
T H
TH
Schroeder
F
F
D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D004735:Energy Transfer; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D005456:Fluorescent Dyes; D006801:Humans; D050356:Lipid Metabolism; D018996:Myelin P2 Protein / Q000378:metabolism; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010940:Plant Proteins; D051381:Rats; D011994:Recombinant Proteins; D013050:Spectrometry, Fluorescence; D025521:Tumor Suppressor Proteins
D002352:Carrier Proteins; C493319:FABP1 protein, human; C107608:FABP7 protein, human; 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; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins; D025521:Tumor Suppressor Proteins; C072087:sterol carrier proteins; C013641:parinaric acid