A protein gives, under conditions of buffer composition, pH, and temperature that are close to physiological conditions, a molecular weight by size exclusion 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 (BME), 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 stoichiometry of subunits, and the kinds of bonding (covalent, non covalent) existing between subunits.

0 BME BME STD Serum albumin 67,000 2 Ovalbumin 43,000 Carbonic anhydrase, 0.000 8 Trypsin inhibitor 20.000 10