Serum Retinol Binding Protein 4 (human recombinant)

Human serum retinol binding protein 4 (sRBP4) binds to one equivalent of vitamin A and is one of the major retinol carriers found in the blood of mammals.{14372,14373} Human sRBP4 is a monomeric 21 kDa ?-sheet-rich protein that contains three disulfide bonds and belongs to the lipocalin protein family.{14379} In plasma, sRBP4 typically forms a 1:1 complex with the 55 kDa tetrameric protein transthyretin (TTR) which prevents RBP from being removed from the plasma by glomerular filtration.{14378} Recent studies have shown that sRBP4 is an adipocyte-derived “signal” that may contribute to the pathogenesis of type 2 diabetes.{14371,14380} Elevation of sRBP4 causes systemic insulin resistance, whereas reduced serum concentrations of sRBP4 improves insulin action.{14371,14376,14374} Cayman’s human recombinant sRBP4 contains a C-terminal hexahistidine tag. The purified protein was characterized for its retinol binding activity.