Different stabilities of the N- and C- terminal domains of human interferon alpha

The present results are consistent with the hypothesis predicting two structurally independent polypeptide domains in the regions 1-92 and 111-166 of the type I IFNs. However, we observed differences in molecular unfolding between the N- and C-terminal portions of human IFN-alpha during denaturation in SDS solutions. Monoclonal antibodies (mAbs) detected changes in the N-terminal region (residues 1-85) of denaturated IFN-alpha 1 or IFN-alpha 2. In contrast, SDS-denaturation of antigens did not affect the reactivity of mAbs with epitopes located in the C-terminal portion (residues 105-166) of both IFNs. The N-terminal domain is known to be involved in the high affinity receptor binding of IFN-alpha. Therefore a theory that the active sites may be conformationally more flexible than the rest of the polypeptide might explain the lower conformational stability of this domain.