Institut de Biotecnologia i de Biomedicina and Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Bellaterra (Barcelona), Spain.
Proteomics. 2010 Dec;10(23):4172-85. doi: 10.1002/pmic.201000260.
The formation of insoluble deposits by globular proteins underlies the onset of many human diseases. Recent studies suggest a relationship between the thermodynamic stability of proteins and their in vivo aggregation. However, it has been argued that, in the cell, the occurrence of irreversible aggregation might shift the system from equilibrium, in such a way that it could be the rate of unfolding and associated kinetic stability instead of the conformational stability that controls protein deposition. This is an important but difficult to decipher question, because kinetic and thermodynamic stabilities appear usually correlated. Here we address this issue by comparing the in vitro folding kinetics and stability features of a set of non-natural SH3 domains with their aggregation properties when expressed in bacteria. In addition, we compare the in vitro stability of the isolated domains with their effective stability in conditions that mimic the cytosolic environment. Overall, the data argue in favor of a thermodynamic rather than a kinetic control of the intracellular aggregation propensities of small globular proteins in which folding and unfolding velocities largely exceed aggregation rates. These results have implications regarding the evolution of proteins.
球状蛋白形成不溶性沉积物是许多人类疾病的开始。最近的研究表明，蛋白质的热力学稳定性与它们在体内聚集之间存在关系。然而，有人认为，在细胞中，不可逆聚集的发生可能会使系统偏离平衡，以至于控制蛋白质沉积的可能是展开的速率和相关的动力学稳定性，而不是构象稳定性。这是一个重要但难以解读的问题，因为动力学和热力学稳定性通常是相关的。在这里，我们通过比较一组非天然 SH3 结构域的体外折叠动力学和稳定性特征及其在细菌中表达时的聚集特性来解决这个问题。此外，我们还比较了分离结构域的体外稳定性与其在模拟细胞溶质环境的条件下的有效稳定性。总的来说，这些数据支持在折叠和展开速度大大超过聚集速率的小球状蛋白质的细胞内聚集倾向受热力学控制而不是动力学控制。这些结果对蛋白质的进化具有重要意义。
