抄録
Binding properties of the rat liver cytoplasmic organic anion binding proteins, Y and Z proteins, for two organic anionic model compounds, bromphenol blue (BPB) and amaranth (AM) which are transported from blood stream into the rat bile by an active transport system, were studied by means of chemical methods, modifying the proteins with sulfhydryl-blocking reagents and amino group modifiers and fluorescent probe. Moreover, the affinities to Y and Z proteins were compared with that to bovine serum albumin by means of the apparent association constants. AM had higher affinity to the liver proteins than to bovine serum albumin, but in the case of BPB reverser result was obtained. The hydrophobic binding is important for the bindings of the dyes to the both proteins and BPB had higher affinities to the both proteins than AM. However, the binding properties to the both proteins were different, namely the binding of AM to Y protein was thought to be mainly due to the hydrophobic forces but the contribution of ionic forces could not be neglected with respect to the binding of BPB to the both protems.
