RESUMO

The family of the liver bile acid-binding proteins (L-BABPs), formerly called liver basic fatty acid-binding proteins (Lb-FABPs) shares fold and sequence similarity with the paralogous liver fatty acid-binding proteins (L-FABPs) but has a different stoichiometry and specificity of ligand binding. This article describes the first X-ray structure of a member of the L-BABP family, axolotl (Ambystoma mexicanum) L-BABP, bound to two different ligands: cholic and oleic acid. The protein binds one molecule of oleic acid in a position that is significantly different from that of either of the two molecules that bind to rat liver FABP. The stoichiometry of binding of cholate is of two ligands per protein molecule, as observed in chicken L-BABP. The cholate molecule that binds buried most deeply into the internal cavity overlaps well with the analogous bound to chicken L-BABP, whereas the second molecule, which interacts with the first only through hydrophobic contacts, is more external and exposed to the solvent.

Assuntos

Proteínas de Transporte/química , Proteínas de Transporte/metabolismo , Ácido Cólico/metabolismo , Fígado/metabolismo , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/metabolismo , Ácido Oleico/química , Ácido Oleico/metabolismo , Ambystoma , Sequência de Aminoácidos , Animais , Ácidos e Sais Biliares/metabolismo , Proteínas de Transporte/isolamento & purificação , Cristalografia por Raios X , Proteínas de Ligação a Ácido Graxo/química , Proteínas de Ligação a Ácido Graxo/metabolismo , Glicoproteínas de Membrana/isolamento & purificação , Modelos Moleculares , Conformação Proteica , Estrutura Secundária de Proteína , Ratos , Soluções