Pathway of Oxidative Folding of Bovine α-Interferon:  Predominance of Native Disulfide-Bonded Folding Intermediates

• Published in: Biochemistry (Easton) Vol. 46; no. 12; pp. 3925 - 3932
• Main Authors: Lin, Curtis C.-J., Chang, Jui-Yoa
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 27.03.2007
• Subjects: Animals; Cattle; Disulfides - chemistry; Interferon-alpha - chemistry; Isomerism; Models, Molecular; Oxidation-Reduction; Protein Folding; Protein Structure, Secondary; Protein Structure, Tertiary
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi0623126

Bovine α-interferon (BoINF-α) is a single polypeptide protein containing 166 amino acids, two disulfide bonds (Cys1−Cys99 and Cys29−Cys138), and five stretches of α-helical structure. The pathway of oxidative folding of BoINF-α has been investigated here. Of the eight possible one- and two-disulfide isomers, only two nativelike one-disulfide isomers, BoINF-α (Cys1−Cys99) and BoINF-α (Cys29−Cys138), predominate as intermediates along the folding pathway. More strikingly, α-helical structures formed almost quantitatively before any detectable formation of a disulfide bond. This is demonstrated by the observation that fully reduced BoINF-α (starting material of oxidative folding) and reduced carboxymethylated BoINF-α both exhibit α-helical structure content indistinguishable form that of native BoINF-α. The folding mechanism of BoINF-α appears to be compatible with the framework model, in which secondary structures fold first, followed by docking (compaction) of preformed secondary structural elements yielding the native structure.