Membrane Protein Stability

项目摘要 膜蛋白在许多细胞过程中起着至关重要的作用。总目标 这项研究的目的是了解蛋白质折叠过程的物理基础 以及膜蛋白结构的生物物理基础。目前，这两个都不是 对于膜蛋白是很好理解的。 从热力学上讲，我们的工作解决了疏水性在 膜蛋白折叠。在之前的授权期，我们开发了一部小说 疏水性标度，测量侧链从水到分子的转移自由能 膜中心使用一个真正的双层和一个真正的折叠的膜蛋白。基于 这一成就，我们现在建议通过测量来检验该量表(1)的通用性 使用不同的膜蛋白支架的侧链转移自由能； 确定双分子层中的埋藏程度如何将水调节为双分子层自由转移 能量；以及(3)通过设计我们的蛋白质支架来作为功能进行测量 以解决可电离基团突变的能量后果是如何变化的 处于带电状态。 从动力学上讲，我们在前一次资助期间发现，大肠杆菌脂头基团 可能起到能量势的作用，将膜蛋白从错误中分离出来 (内)膜并朝向正确的(外)膜位置。我们建议 第四个目的是通过确定 E.诱导折叠的动力学寿命、构象和激活能。 含有大肠杆菌的脂头基团。

Project Summary Membrane proteins play essential roles in many cellular processes. The overall goal of the proposed research is to understand the physical basis the protein folding process and the biophysical basis of membrane protein structures. At present, neither of these is well understood for membrane proteins. Thermodynamically, our work addresses the critical role that hydrophobicity plays in membrane protein folds. In the previous granting period, we developed a novel hydrophobicity scale that measures side-chain transfer free energies from water to the membrane center using a real bilayer and a real, folded membrane protein. Based on this achievement, we now propose to test the generality of this scale (1) By measuring side-chain transfer free energies using distinct membrane protein scaffolds; (2) By determining how extent-of-burial in the bilayer modulates water to bilayer transfer free energies; and (3) By engineering of our protein scaffold for measurements as a function of pH to address how the energetic consequences of ionizable group mutations vary with charge state. Kinetically, we discovered in the previous grant period that E. coli lipid head groups may act as energetic potentials that sort membrane proteins away from the wrong (inner) membranes and towards the correct (outer) membrane locations. We propose in a fourth aim to dissect the biophysical basis for this sorting by determining the kinetic lifetimes and conformations and activation energies to folding induced by E. coli-containing lipid head groups.