A protein gives, under conditions of buffer composition, pH, and temperature that are clos...

A protein gives, under conditions of buffer composition, pH, and temperature that are close to physiological conditions, a molecular weight by sedimentation equilibrium measurements of 140,000 g/mol, When the same protein is studied by SDS gel electrophoresis in the absence or presence of the reducing agent β-mercaptoethanol (BMF.), the patterns seen, respectively, in lanes A and B are observed. Lane C contains standards of molecular weight indicated. From these data, describe the native protein, in terms of the kinds of subunits present, the stoi-chiometry of subunits, and the kinds of bonding (covalent, noncovalent) existing between subunits. (See Tools of Biochemistry 6B.)