ABSTRACT
The physicochemical nature of the circulating receptor was clarified by biochemical studies involving specific monoclonal antibodies.
The circulating soluble receptor was purified from human serum and biochemically characterized. The serum receptor exhibited a molecular weight of 85 kDa on SDS-PAGE analysis under both non-reducing and reducing conditions. Amino terminal sequence analysis showed that residues 1 through 19 of the soluble serum receptor were identical to residues 101 through 119 of the membrane-bound receptor. This finding clearly indicates that the circulating receptor is a truncated form that lacks the cytoplasmic and transmembrane domains of the intact membrane-bound receptor (see Figure 6.1).
