Lin Curtis C-J, Chang Jui-Yoa
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.
Biochemistry. 2007 Mar 27;46(12):3925-32. doi: 10.1021/bi0623126. Epub 2007 Mar 1.
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.
牛α-干扰素（BoINF-α）是一种由166个氨基酸组成的单链多肽蛋白，含有两个二硫键（Cys1-Cys99和Cys29-Cys138）以及五个α-螺旋结构区域。本文对BoINF-α的氧化折叠途径进行了研究。在八种可能的单二硫键和二二硫键异构体中，只有两种类似天然的单二硫键异构体，即BoINF-α（Cys1-Cys99）和BoINF-α（Cys29-Cys138），在折叠途径中作为中间体占主导地位。更引人注目的是，在任何可检测到的二硫键形成之前，α-螺旋结构几乎已经定量形成。这一点通过以下观察得到证明：完全还原的BoINF-α（氧化折叠的起始材料）和还原的羧甲基化BoINF-α都表现出与天然BoINF-α难以区分的α-螺旋结构含量。BoINF-α的折叠机制似乎与框架模型相符，在该模型中，二级结构先折叠，然后是预先形成的二级结构元件对接（压实）形成天然结构。
