Irún M P, Garcia-Mira M M, Sanchez-Ruiz J M, Sancho J
Departamento de Bioquímica y Biología Molecular y Celular Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, 50009, Spain.
J Mol Biol. 2001 Mar 2;306(4):877-88. doi: 10.1006/jmbi.2001.4436.
The structure and energetics of protein-folding intermediates are poorly understood. We have identified, in the thermal unfolding of the apoflavodoxin from Anabaena PCC 7119, an equilibrium intermediate with spectroscopic properties of a molten globule and substantial enthalpy and heat capacity of unfolding. The structure of the intermediate is probed by mutagenesis (and phi analysis) of polar residues involved in surface-exposed hydrogen bonds connecting secondary-structure elements in the native protein. All hydrogen bonds analysed are formed in the molten globule intermediate, either with native strength or debilitated. This suggests the overall intermediate's topology and surface tertiary interactions are close to native, and indicates that hydrogen bonding may contribute significantly to shape the conformation and energetics of folding intermediates.
蛋白质折叠中间体的结构和能量学仍知之甚少。我们在来自鱼腥藻PCC 7119的脱辅基黄素氧还蛋白的热解折叠过程中，鉴定出一种平衡中间体，它具有熔球态的光谱特性以及可观的解折叠焓和热容。通过对天然蛋白质中连接二级结构元件的表面暴露氢键所涉及的极性残基进行诱变（和φ分析），来探究该中间体的结构。分析的所有氢键在熔球态中间体中均已形成，强度要么与天然状态相同，要么有所减弱。这表明整体中间体的拓扑结构和表面三级相互作用与天然状态接近，并表明氢键可能对折叠中间体的构象和能量学形成有显著贡献。
