title: Roles of the 29-138 disulfide bond of subtype A of human alpha interferon in its antiviral activity and conformational stability.
abstract: Human alpha (leukocyte) interferons contain two disulfide bonds between Cys-1 and Cys-98 and between Cys-29 and Cys-138. Reduction of interferon under native conditions leads to irreversible loss of antiviral activity; reduction in denaturant, followed by oxidation in native conditions, leads to restoration of activity. This behavior, unusual for disulfide-containing proteins, was studied by using a thiosulfonate derivative of subtype A of human alpha interferon (IFN-alpha A). The disulfide-free thiosulfonate formed at 25 degrees C has essentially no antiviral activity, while maintaining a conformation related to that of native IFN-alpha A. This species can regain activity after regeneration of its 29-138 disulfide, by thiol-disulfide interchange in native buffer. Incubation of the disulfide-free thiosulfonate under nonreducing conditions at 37 degrees C generates a monomeric species that has lost its native conformation as well as its ability to regain antiviral activity after thiol-disulfide interchange. These results explain the difficulty in obtaining, under native conditions, a reduced species that regains activity upon oxidation; complete reduction of IFN-alpha A in 100 mM 2-mercaptoethanol requires 37 degrees C, a temperature that promotes conformational decay of the disulfide-free form.
mesh_terms: D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002942:Circular Dichroism; D004220:Disulfides / Q000032:analysis; D004355:Drug Stability; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007370:Interferon Type I / Q000633:toxicity*; D007668:Kidney; D011487:Protein Conformation; D014721:Vesicular stomatitis Indiana virus / Q000187:drug effects*
chemical_list: D004220:Disulfides; D007370:Interferon Type I