title: Homology of beta-lactoglobulin, serum retinol-binding protein, and protein HC.
abstract: The milk protein beta-lactoglobulin has been extensively studied but its function has not been identified. A clue regarding the function of a protein can be obtained by discovering a genetic relationship with a protein of known function through comparisons of amino acid sequence. Such comparisons revealed that beta-lactoglobulin is similar to human serum retinol-binding protein and to another human protein of unknown function known as complex-forming glycoprotein heterogeneous in charge (protein HC). beta-Lactoglobulins from several species have been found to bind retinol, while the absorption and fluorescence properties reported for the unidentified heterogeneous prosthetic group of protein HC are retinoid-like. The role of serum retinol-binding protein in vitamin A transport in the circulation suggests that the other two homologous proteins may function in the binding and transport of retinoids; beta-lactoglobulin may facilitate the absorption of vitamin A from milk and protein HC may mediate the excretion of retinol-derived metabolites.
authors.forename: S
authors.initials: S
authors.lastname: Pervaiz
authors.forename: K
authors.initials: K
authors.lastname: Brew
mesh_terms: D000510:Alpha-Globulins / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D004289:Dolphins; D006801:Humans; D007782:Lactoglobulins / Q000235:genetics* / Q000378:metabolism; D007793:Lagomorpha; D008322:Mammals; D008892:Milk / Q000378:metabolism; D011323:Primates; D011487:Protein Conformation; D011507:Proteinuria / Q000378:metabolism; D012177:Retinol-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D012377:Rodentia; D013552:Swine; D014801:Vitamin A / Q000378:metabolism
chemical_list: D000510:Alpha-Globulins; D007782:Lactoglobulins; D012177:Retinol-Binding Proteins; C016001:alpha-1-microglobulin; D014801:Vitamin A