Physicochemical and immunochemical properties of γ1 heavy chain disease protein baz

Abstract The physicochemical and antigenic properties of a γ1 heavy chain disease protein (γl HCD BAZ) are described. Protein BAZ is positive for the Glm(1) determinant and gives a reaction of identity with Fc fragment, whether derived from Cohn Fraction II or from an IgG1 myeloma protein. It also gives a reaction of complete identity with the γHCD proteins CRA and ZUC. The mol. wt of the native protein was determined from (1) sedimentation-diffusion, (2) sedimentation-viscosity, and (3) sedimentation-equilibrium measurements to be approx 60,000 daltons. The mol. wt of the unreduced protein in 6 M guanidine hydrochloride was found to be 30,000 daltons, which was identical to that of the reduced-alkylated form in 6 M guanidine. These results established that γ1 HCD BAZ is a noncovalently linked dimer and suggested the possibility of a missing hinge region.