IDENTIFICATION OF BINDING-PROTEINS INVOLVED IN THE STAGE-SPECIFIC UPTAKE OF ARYLPHORIN BY THE FAT-BODY CELLS OF CALLIPHORA-VICINA

The larval serum protein arylphorin of Calliphora vicina is stage-specifically and selectively taken up from the haemolymph by the fat body cells of late larvae and white puparia. We give evidence for specific arylphorin binding sites in a membrane fraction referring to the characteristics of a "receptor". Scatchard plot analysis revealed the existence of more than one binding site. By means of a combined ligand-immunoblotting method we identified three arylphorin binding proteins with apparent molecular weights of 65, 96, and 130 kDa. These polypeptides exhibit different patterns of appearance throughout the last larval instar.