Prouty M S, Schechter A N, Parsegian V A
J Mol Biol. 1985 Aug 5;184(3):517-28. doi: 10.1016/0022-2836(85)90298-0.
We have used the "osmotic stress" method to determine the phase diagram of deoxyhemoglobin S polymerization. This method involves equilibration, through a semipermeable membrane, of the protein with solutions of inert polymers of known osmotic pressure. With deoxyhemoglobin A and S solutions, in which we have demonstrated achievement of equilibrium, plots of osmotic pressure versus concentration initially agree closely with the results of other methods of measurement of colligative properties. However, once the known solubility value is exceeded for the deoxyhemoglobin S solutions at various temperatures, there is a rapid rise in hemoglobin concentration over a narrow osmotic pressure range and then a more gradual increase in concentration. We believe that these two regions correspond, respectively, to the onset of the polymerization process, and of subsequent continuing growth and compression or alignment of polymer. We derive the thermodynamic values for these processes and show that the behavior of the deoxyhemoglobin S system is analogous to the phase transition for a simple chemical system. These results are relevant to understanding the intracellular polymerization of deoxyhemoglobin S in sickle cell disease, and these concepts are applicable to other protein assembly systems.
我们已使用“渗透压应激”方法来确定脱氧血红蛋白S聚合的相图。该方法涉及通过半透膜使蛋白质与已知渗透压的惰性聚合物溶液达到平衡。对于脱氧血红蛋白A和S溶液，我们已证明达到了平衡，渗透压与浓度的关系图最初与其他依数性测量方法的结果非常吻合。然而，一旦在不同温度下脱氧血红蛋白S溶液超过了已知的溶解度值，在狭窄的渗透压范围内血红蛋白浓度会迅速上升，然后浓度逐渐增加。我们认为这两个区域分别对应聚合过程的开始，以及随后聚合物的持续生长和压缩或排列。我们推导了这些过程的热力学值，并表明脱氧血红蛋白S系统的行为类似于简单化学系统的相变。这些结果对于理解镰状细胞病中脱氧血红蛋白S的细胞内聚合具有重要意义，并且这些概念适用于其他蛋白质组装系统。
