Binding of recombinant rat liver fatty acid-binding protein to small anionic phospholipid vesicles results in ligand release: a model for interfacial binding and fatty acid targeting.
A number of intracellular proteins bind to negatively charged phospholipid membranes, and this interfacial binding results in a conformational change that modulates the activity of the protein. Using a fluorescent fatty acid analogue, 11-[5-(dimethylamino)naphthalenesulfonyl]undecanoic acid (DAUDA), it is possible to demonstrate the release of this ligand from recombinant rat liver FABP in the presence of phospholipid vesicles that contain a significant proportion of anionic phospholipids. The ligand release that is observed with anionic phospholipids is sensitive to the ionic strength of the assay conditions and the anionic charge density of the phospholipid at the interface, indicating that nonspecific electrostatic interactions play an important role in the process. The stoichiometric relationship between anionic phospholipid and liver FABP suggests that the liver FABP coats the surface of the phospholipid vesicle. The most likely explanation for ligand release is that interaction of FABP with an anionic membrane interface induces a rapid conformational change, resulting in a reduced affinity of DAUDA for the protein. The nature of this interaction involves both electrostatic and nonpolar interactions as maximal release of liver FABP from phospholipid vesicles with recovery of ligand binding cannot be achieved with high salt and requires the presence of a nonionic detergent. The precise interfacial mechanism that results in the rapid release of ligand from L-FABP remains to be determined, but studies with two mutants, F3W and F18W, suggest the possible involvement of the amino-terminal region of the protein in the process. The conformational change linked to interfacial binding of this protein could provide a mechanism for fatty acid targeting within the cell.
Davies
J K
JK
Division of Biochemistry and Molecular Biology, University of Southampton, United Kingdom.
Thumser
A E
AE
Wilton
D C
DC
D000818:Animals; D000838:Anions / Q000737:chemistry / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D003619:Dansyl Compounds / Q000737:chemistry; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D008099:Liver / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D018996:Myelin P2 Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010715:Phosphatidylglycerols / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D055672:Static Electricity; D014364:Tryptophan / Q000235:genetics
D000838:Anions; D002352:Carrier Proteins; D003619:Dansyl Compounds; 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; D005456:Fluorescent Dyes; D008024:Ligands; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010715:Phosphatidylglycerols; D010743:Phospholipids; D011994:Recombinant Proteins; C051388:1,2-dioleoyl-sn-glycero-3-phosphoglycerol; C054400:11-(dansylamino)undecanoic acid; D014364:Tryptophan