Solution Structure and Backbone Dynamics of Human Liver Fatty Acid Binding Protein

Abstract

Liver Fatty Acid Binding Protein (L-FABP), a small (14 kDa) cytosolic protein most abundant in liver, performs several putative functions, including intracellular transport of fatty acids, nuclear signaling, and regulation of intracellular lipolysis. Among the various members of the intracellular lipid binding protein (iLBP) family, L-FABP is of particular interest, as it can bind more than one FA molecule at the same time and furthermore binds a large variety of other bulkier physiological ligands such as bilirubin and acyl CoA. To better understand these promiscuous binding and transport properties of L-FABP, we have applied multi-dimensional NMR spectroscopy for studies of its structure and backbone dynamics with and without the presence of ligands. The overall conformation of human L-FABP, as determined from NOE-derived distance restraints, shows a very typical b-clam motif comprised of 10 anti-parallel b-strands that are covered by 2 short nearly parallel a-helices. However, backbone dynamics of human L-FABP probed by hydrogen/deuterium exchange and 15N relaxation measurements exhibit a conformational flexibility and backbone mobility that is remarkably different to that of other iLBPs. We hypothesize that the higher conformational flexibility of L-FABP helps to accommodate bulky ligands inside the binding cavity. Moreover, this structure and dynamic information of human L-FABP broadens our current understanding of the iLBP family and helps to explain its diversity and functional differences.