Structural Constraints on Subunit Assembly

通常认为，作为多亚单位复合体的组成部分的多肽具有相同的结构，无论是在复合体中还是作为游离亚单位。这一提议所基于的假设是，这种观点通常并不准确。这一等电点表明，复合体中亚基的构象可能只代表游离亚单位的平衡群体中存在的一小部分构象。支持这一假设的事实是，组装多亚单位络合物的缔合速率常数跨越许多数量级的值。通过这项建议中描述的实验，PI期望发现荧光素酶亚基的相关速率的动力学异质性。缔合率的差异将是不同结构的证据，不同速率分量的相对幅度将允许定量描述构象的相对种群。在这些实验的第二阶段，PI将确定溶液条件和遗传突变可能在多大程度上改变异构体的数量。活细胞中的大部分多肽都在多亚单位复合体中发挥作用。人们对这些复合体组装的基本机制知之甚少。人们对络合物形成的能量学进行了广泛的研究，但对络合物的形成和解离速率的研究相对较少。蛋白质之间的相互作用在许多基本的生命过程中起着至关重要的作用。这一项目的研究旨在更详细和更基本地了解多亚基蛋白质的动态性质。

0078363Baldwin, ThomasIt is commonly assumed that polypeptides that function as components of multisubunit complexes have the same structure, whether in the complex or as the free subunit. The hypothesis upon which this proposal is based is that this view is not generally accurate. This PI suggest that the conformation of the subunit in the complex may represent only a fraction of the conformations present in an equilibrium population of the free subunits. In support of this hypothesis is the fact that the associate rate constants for assembly of multisubunit complexes span many orders of magnitude in value. Through the experiments described in this proposal, the PI expects to find kinetic heterogeneity in associate rates for the luciferase subunits. Differences in association rates will be evidence for differing structures, and the relative amplitudes of the different rate components will allow quantitative description of the relative populations of conformers. In the second phase of these experiments, the PI will ascertain the extent to which the populations of conformers may be altered by solution conditions and by genetic mutation.A large proportion of all polypeptides in living cells function within multisubunit complexes. The fundamental mechanisms through which these complexes assemble are very poorly understood. There has been extensive work on the energetics of complex formation, but relatively little on the rates of formation and dissociation. Protein-protein interactions play crucial roles in many fundamental life processes. The research of this project is designed to obtain a more detailed and fundamental understanding of the dynamic nature of multisubunit proteins.