In Vitro Oxidation of Intrinsic Sulfhydryl Groups Yields Polymers of the Two Predominant Polypeptides in the Nuclear Envelope Fraction

The two quantitatively predominant nuclear nonhistone polypeptides of the avian erythrocyte comprise a significant portion of the nuclear envelope protein. Each of these two polypeptides can be converted almost completely to homogeneous polymeric species via oxidation of intrinsic sulfhydryl groups by o-phenanthroline cupric ion complex. Major products are two dimeric species arising from each of the approximately 77 000-dalton pair. The larger of the two polypeptides also yields oligomers greater than dimers. These observations extend our earlier solubility and polypeptide cross-linking evidence which indicated that these polypeptides were involved in an oligomeric, proteinaceous nuclear structure. Ultramicroscopic studies from other laboratories indicate that such a structure may function as a nuclear skeleton. The architectural details of the structure now appear to be accessible at the molecular level.