Surewicz W K, Olesen P R
Mason Institute of Ophthalmology, University of Missouri, Columbia 65212, USA.
Biochemistry. 1995 Aug 1;34(30):9655-60. doi: 10.1021/bi00030a001.
alpha-Crystallin is a major structural protein of the vertebrate lens which shows structural and functional similarities to small heat shock proteins. The structure and the thermal stability of bovine alpha-crystallin were studied by Fourier-transform infrared spectroscopy, circular dichroism, and differential scanning calorimetry. Infrared spectroscopic data provide evidence which corroborates the view that the secondary structure of alpha-crystallin is highly ordered and consists predominantly of beta-sheets. However, the present results fail to support the widespread notion of an extremely high thermal stability of the protein. All three experimental approaches used in this study show that alpha-crystallin undergoes a major thermotropic transition with a midpoint at 60-62 degrees C. Furthermore, Fourier-transform infrared spectra provide evidence that this conformational transition is associated with a massive loss of the native beta-sheet structure. These results shed new light on structural properties of alpha-crystallin and have important implications for understanding the mechanism of the chaperone-like action of this protein.
α-晶状体蛋白是脊椎动物晶状体的一种主要结构蛋白，它在结构和功能上与小分子热休克蛋白相似。利用傅里叶变换红外光谱、圆二色光谱和差示扫描量热法研究了牛α-晶状体蛋白的结构和热稳定性。红外光谱数据提供的证据支持了α-晶状体蛋白二级结构高度有序且主要由β-折叠组成的观点。然而，目前的结果未能支持该蛋白质具有极高热稳定性这一广泛观点。本研究中使用的所有三种实验方法均表明，α-晶状体蛋白经历了一个主要的热致转变，转变中点在60 - 62摄氏度。此外，傅里叶变换红外光谱提供的证据表明，这种构象转变与天然β-折叠结构的大量丧失有关。这些结果为α-晶状体蛋白的结构特性提供了新的认识，并对理解该蛋白的伴侣样作用机制具有重要意义。
