Department of Biotechnology and Biosciences, Piazza della Scienza 2, University of Milano-Bicocca, 20126, Milan, Italy.
J Mass Spectrom. 2013 Aug;48(8):895-903. doi: 10.1002/jms.3237.
Human liver fatty acid binding protein (hL-FABP) is the most abundant cytosolic protein in the liver. This protein plays important roles associated to partitioning of fatty acids (FAs) to specific metabolic pathways, nuclear signaling and protection against oxidative damage. The protein displays promiscuous binding properties and can bind two internal ligands, unlike FABPs from other tissues. Different topologies for the ligand located in the more accessible site have been reported, with either a 'head-in' or 'head-out' orientation of the carboxylate end. Electrospray-ionization mass spectrometry and nuclear magnetic resonance titrations are employed here in order to investigate in further detail the binding properties of this system, the equilibria established in solution and the pH dependence of the complexes. The results are consistent with two binding sites with different affinity and a unique head-out topology for the second molecule of either ligand. Competition experiments indicate a higher affinity for oleic acid relative to palmitic acid at each binding site.
人肝脂肪酸结合蛋白（hL-FABP）是肝脏中含量最丰富的胞质蛋白。该蛋白在将脂肪酸（FAs）分配到特定代谢途径、核信号转导和防止氧化损伤方面发挥着重要作用。该蛋白具有混杂的结合特性，能够结合两种内源性配体，这与来自其他组织的 FABPs 不同。已有报道称，位于更易接近部位的配体具有不同的拓扑结构，羧基末端呈“头入”或“头出”取向。本文采用电喷雾电离质谱和核磁共振滴定法，以进一步研究该体系的结合特性、溶液中建立的平衡以及配合物的 pH 依赖性。结果与两个具有不同亲和力的结合位点一致，并且对于任一配体的第二个分子，均具有独特的头出拓扑结构。竞争实验表明，在每个结合位点，油酸相对于棕榈酸具有更高的亲和力。
