Physicochemical and immunochemical properties of γ1 heavy chain disease protein baz

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 6M guanidine hydrochloride was found to be 30,000 daltons, which was identical to that of the reduced-alkylated form in 6M guanidine. These results established that γ1 HCD BAZ is a noncovalently linked dimer and suggested the possibility of a missing hinge region.