Przybycien T M, Bailey J E
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125.
Biochim Biophys Acta. 1991 Jan 8;1076(1):103-11. doi: 10.1016/0167-4838(91)90226-p.
The secondary structure implications of precipitation induced by a chaotropic salt, KSCN, and a structure stabilizing salt, Na2SO4, were studied for twelve different proteins. alpha-helix and beta-sheet content of precipitate and native structures were estimated from the analysis of amide I band Raman spectra. A statistical analysis of the estimated perturbations in the secondary structure contents indicated that the most significant event is the formation of beta-sheet structures with a concomitant loss of alpha-helix on precipitation with KSCN. The conformational changes for each protein were also analyzed with respect to elements of primary, secondary and tertiary structure existing in the native protein; primary structure was quantified by the fractions of hydrophobic and charged amino acids, secondary structure by x-ray estimates of alpha-helix and beta-sheet contents of native proteins and tertiary structure by the dipole moment and solvent-accessible surface area. For the KSCN precipitates, factors affecting beta-sheet content included the fraction of charged amino acids in the primary sequence and the surface area. Changes in alpha-helix content were influenced by the initial helical content and the dipole moment. The enhanced beta-sheet contents of precipitates observed in this work parallel protein structural changes occurring in other aggregative phenomena.
研究了促溶剂KSCN和结构稳定剂Na₂SO₄诱导沉淀对12种不同蛋白质二级结构的影响。通过分析酰胺I带拉曼光谱估算沉淀和天然结构中的α螺旋和β折叠含量。对二级结构含量估算扰动的统计分析表明，最显著的事件是在KSCN沉淀时形成β折叠结构，同时α螺旋减少。还针对天然蛋白质中存在的一级、二级和三级结构元素分析了每种蛋白质的构象变化；一级结构通过疏水和带电荷氨基酸的比例量化，二级结构通过天然蛋白质α螺旋和β折叠含量的X射线估算量化，三级结构通过偶极矩和溶剂可及表面积量化。对于KSCN沉淀，影响β折叠含量的因素包括一级序列中带电荷氨基酸的比例和表面积。α螺旋含量的变化受初始螺旋含量和偶极矩的影响。在这项工作中观察到的沉淀中β折叠含量增加与其他聚集现象中发生的蛋白质结构变化相似。
