title: Molecular simulations of β-lactoglobulin complexed with fatty acids reveal the structural basis of ligand affinity to internal and possible external binding sites.
abstract: The interaction of saturated fatty acids of different length (C8:0 to C18:0) with β-lactoglobulin (βLG) was investigated by molecular dynamics simulation and docking approaches. The results show that the presence of such ligands in the hydrophobic central cavity of βLG, known as the protein calyx, determines an enhancement of atomic fluctuations compared with the unliganded form, especially for loops at the entrance of the binding site. Concerted motions are evidenced for protein regions that could favor the binding of ligands. The mechanism of anchoring of fatty acids of different length is similar for the carboxylate head-group, through electrostatic interactions with the side chains of Lys60/Lys69. The key protein residues to secure the hydrocarbon chain are Phe105/Met107, which adapt their conformation upon ligand binding. In particular, Phe105 provides an additional hydrophobic clamp only for the tail of the two fatty acids with the longest chains, palmitic, and stearic acid, which are known to bind βLG with a high affinity. The search of additional external binding sites for fatty acids, distinct from the calyx, was also carried out for palmitic acid. Two external sites with a lower affinity were identified as secondary sites, one consisting in a hydrophobic cavity allowing two distinct binding modes for the fatty acid, and the other corresponding to a surface crevice close to the protein α-helix. The overall results provide a comprehensive picture of the dynamical behavior of βLG in complex with fatty acids, and elucidate the structural basis of the binding of these physiological ligands.
authors.affiliation: Department of Physics, University of Calabria, Ponte P. Bucci, Cubo 31C, 87036, Rende (CS), Italy; CNR-IPCF UOS of Cosenza, LiCryL and CEMIF.Cal, University of Calabria, Ponte P. Bucci, Cubo 33B, 87036, Rende (CS), Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Evoli
authors.forename: Rita
authors.initials: R
authors.lastname: Guzzi
authors.forename: Bruno
authors.initials: B
authors.lastname: Rizzuti
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D005230:Fatty Acids, Nonesterified / Q000737:chemistry* / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D007782:Lactoglobulins / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008239:Lysine / Q000737:chemistry; D008715:Methionine / Q000737:chemistry; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D008970:Molecular Weight; D019308:Palmitic Acid / Q000737:chemistry / Q000378:metabolism; D010649:Phenylalanine / Q000737:chemistry; D011487:Protein Conformation; D055672:Static Electricity; D013229:Stearic Acids / Q000737:chemistry / Q000378:metabolism; D013499:Surface Properties
chemical_list: D005230:Fatty Acids, Nonesterified; D007782:Lactoglobulins; D008024:Ligands; D013229:Stearic Acids; D019308:Palmitic Acid; D010649:Phenylalanine; C031183:stearic acid; D008715:Methionine; D008239:Lysine
keywords: binding sites; fatty acids; molecular docking; molecular dynamics simulation; β-lactoglobulin