lipocalin/cytosolic fatty acid-binding protein family
Lipocalins are diverse, mainly low molecular weight extracellular proteins that bind principally small hydrophobic ligands, and form covalent or non-covalent complexes with soluble macromolecules as well as membrane bound-receptors. They have a large beta-barrel ligand-binding cavity. Members include retinol-binding protein, retinoic acid-binding protein, complement protein C8 gamma, Can f 2, apolipoprotein D, extracellular fatty acid-binding protein, beta-lactoglobulin, oderant-binding protein, and bacterial lipocalin Blc. Lipocalins are involved in many important processes such as ligand transport, modulation of cell growth and metabolism, regulation of immune response, smell reception, tissue development and animal behavior. Cytosolic fatty acid-binding proteins also bind hydrophobic ligands in a non-covalent, reversible manner, and are involved in protection and shuttling of fatty acids within the cell, and in acquisition and removal of fatty acids from intracellular sites.
Comment:hydrophobic cavity binds different hydrophobic ligands; ligands are bound within the beta-barrel in a central internal water-filled cavity lined with polar and hydrophobic amino acids
Jiyao W et al.(2023). "The conserved domain database in 2023.",