Pathway of oxidative folding of bovine alpha-interferon: predominance of native disulfide-bonded folding intermediates.
Bovine alpha-interferon (BoINF-alpha) is a single polypeptide protein containing 166 amino acids, two disulfide bonds (Cys1-Cys99 and Cys29-Cys138), and five stretches of alpha-helical structure. The pathway of oxidative folding of BoINF-alpha has been investigated here. Of the eight possible one- and two-disulfide isomers, only two nativelike one-disulfide isomers, BoINF-alpha (Cys1-Cys99) and BoINF-alpha (Cys29-Cys138), predominate as intermediates along the folding pathway. More strikingly, alpha-helical structures formed almost quantitatively before any detectable formation of a disulfide bond. This is demonstrated by the observation that fully reduced BoINF-alpha (starting material of oxidative folding) and reduced carboxymethylated BoINF-alpha both exhibit alpha-helical structure content indistinguishable form that of native BoINF-alpha. The folding mechanism of BoINF-alpha 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.
Lin
Curtis C-J
CC
Research Center for Protein Chemistry, Brown Foundation Institute of Molecular Medicine, and Department of Biochemistry and Molecular Biology, University of Texas, Houston, Texas 77030, USA.
Chang
Jui-Yoa
JY
D000818:Animals; D002417:Cattle; D004220:Disulfides / Q000737:chemistry*; D016898:Interferon-alpha / Q000737:chemistry*; D007536:Isomerism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
D004220:Disulfides; D016898:Interferon-alpha