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.1,2 Human sRBP4 is a monomeric 21 kDa -sheet-rich protein that contains three disulfide bonds and belongs to the lipocalin protein family.3 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.4 Recent studies have shown that sRBP4 is an adipocyte-derived signal that may contribute to the pathogenesis of type 2 diabetes.5,6 Elevation of sRBP4 causes systemic insulin resistance, wherEAs reduced serum concentrations of sRBP4 improves insulin action.5,7,8 Caymans human recombinant sRBP4 contains a C-terminal hexahistidine tag. The purified protein was characterized for its retinol binding activity.Technical InformationSynonymsRBP4sRBP4Purity95%Sourcerecombinant His-tagged protein purified from E. coliMW~21 kDaFormulationA solution in 50 mM sodium phosphate, pH 8.2, containing 100 mM sodium chloride and 20% glycerol