几种盐类对光系统Ⅱ33kD锰稳定蛋白溶液构象的影响

借助内源荧光和圆二色谱分析，考察了几种不同的盐溶液（CaCl2,NaCl,脲，三氯乙酸、二硫苏糖醇）对水溶液中33kD蛋白构象的影响，以295nm波长的乐激发时，33kD蛋白具有330nm的荧光发射峰，表明33kD蛋白所含唯一的^241Trp位于分子内部的疏水部位，CaCl2、脲、三氯乙酸或二硫苏糖醇的存在，均会改变33kD蛋白的内源荧光的强度和位置，而NaCl几科无影响，脲、二硫苏糖醇对33kD蛋白的二级结构的影响较大，因此维系33kD蛋白构象的主要因素包括：二硫键、疏水作用、范得华力和氢键，而离子键的贡献较小。

Effects of several solvents on the conformation of the 33 kD protein of photosystem II

The fluorescence measurement was used to study the effects on the structure of the 33 kD protein of the several solvents including CaCl 2, NaCl, Urea, TCA (trichloroacetate), DTT (dithiothreitol). The results suggest that the 33 kD extrinsic protein possibly has a hydrophobic (-sheet core, in which the 241 Trp is buried, and that most of the aromatic amino acids of the 33 kD protein are located in more hydrophobic environment. Likewise CaCl 2, Urea and TCA can destroy the hydrophobic core of C terminus.Further CD measurement suggests that Urea, DTT can alter the secondary structure of the 33 kD protein dramatically, and NaCl affects that a little. Which leads to loss of the secondary bonds with photosystem II particles and makes the 33 kD protein release from the photosystem II particles. Whereas, NaCl affects a little on the conformation of the protein, so it can not make release of the 33 kD protein from photosystem II. These results also suggest that the native tertiary structure of the 33 kD protein in solution is possibly responsible for its binding to the photosystem II, and that the hydrophobic interaction between C terminus domain with the hydrophobic sheet core is important for 33 kD protein to maintain the native structure.