McHaourab Hassane S, Kumar M Satish, Koteiche Hanane A
Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
FEBS Lett. 2007 May 15;581(10):1939-43. doi: 10.1016/j.febslet.2007.04.005. Epub 2007 Apr 13.
To elucidate the structural and energetic basis of attractive protein interactions in the aging lens, we investigated the binding of destabilized mutants of betaB1-crystallin to the lens chaperones, alpha-crystallins. We show that the mutations enhance the binding affinity to alphaA- but not alphaB-crystallin at physiological temperatures. Complex formation disrupts the dimer interface of betaB1-crystallin consistent with the binding of a monomer. Binding isotherms obtained at increasing concentrations of betaB1-crystallin deviate from a classic binding equilibrium and display cooperative-like behavior. In the context of betaB1-crystallin unfolding equilibrium, these characteristics are reflective of the concentration-dependent change in the population of a dimeric intermediate that has low affinity to alphaA-crystallin. In the lens, where alpha-crystallin binding sites are not regenerated, this may represent an added mechanism to maintain lens transparency.
为阐明老化晶状体中蛋白质吸引相互作用的结构和能量基础，我们研究了βB1-晶状体蛋白的不稳定突变体与晶状体伴侣蛋白α-晶状体蛋白的结合情况。我们发现，在生理温度下，这些突变增强了与αA-晶状体蛋白而非αB-晶状体蛋白的结合亲和力。复合物的形成破坏了βB1-晶状体蛋白的二聚体界面，这与单体的结合情况一致。在βB1-晶状体蛋白浓度增加时获得的结合等温线偏离经典的结合平衡，并表现出类似协同的行为。在βB1-晶状体蛋白的解折叠平衡背景下，这些特征反映了对αA-晶状体蛋白亲和力较低的二聚体中间体群体中浓度依赖性的变化。在晶状体中，α-晶状体蛋白的结合位点不会再生，这可能是维持晶状体透明度的一种额外机制。
