Energetics of Ionizable Groups Buried in Proteins

LattmanMCB 9982967本研究的目标是对葡萄球菌核酸酶和其他蛋白质的突变体进行结构、量热和稳定性研究，其中可电离侧链已深埋在蛋白质的疏水核心中。早期的测量表明，地核中的极性比之前认为的要高得多。这个项目将探索水分子和其他因素作为这种高极性的物理基础的作用，并试图发现在核酸酶中观察到的结果是否可以推广到其他蛋白质。在与Bertrand Garcia-Moreno实验室合作研究的突变体V66E中，X射线晶体结构显示结构中有四个水分子，将谷氨酸侧链与蛋白质表面连接起来。这一观察表明，埋在地下的水分子，无论是有序的还是无序的，可能在提供所观察到的极性方面发挥了作用。大多数生物功能是通过一个蛋白质分子与另一个蛋白质分子结合，或通过一个小分子与蛋白质结合而实现的。例如，当肌动蛋白与肌球蛋白相互作用时，肌肉产生力量，类固醇激素(非蛋白质)通过与类固醇激素受体(蛋白质)结合而发挥影响。创造新催化剂的努力(例如，用于转化石油产品)也取决于对一个分子与另一个分子如何结合的定量理解。稳定这些相互作用的最重要的力之一是静电力。这个关于在蛋白质中植入电荷的项目应该会导致对静电力的更好的理解，因此应该有助于改进这些方法。

LattmanMCB 9982967The objectives of this research are to carry out structural, calorimetric, and stability studies on mutants of staphylococcal nuclease and other proteins in which ionizable sidechains have been buried deep in the protein's hydrophobic core. Earlier measurements have suggested that polarity in the core is much higher than had been previously believed. This project will probe the role of water molecules and other factors as a physical basis for this high polarity and seek to discover whether the observations in nuclease can be generalized to other proteins. In the mutant V66E, studied in collaboration with the laboratory of Bertrand Garcia-Moreno, the X-ray crystal structure shows four water molecules in the structure, connecting the glutamate sidechain with the protein surface. This observation suggests that buried water molecules, ordered or disordered, may play a role in providing the observed polarity. Most biological function comes about through one protein molecule binding to another, or through a small molecule binding to a protein. For example, muscle develops force when actin interacts with myosin, and steroid hormones (non-protein) exert their influence by binding to steroid hormone receptors (proteins). Efforts to create new catalysts (for transforming petroleum products for example) also depend on quantitative understanding of how one molecule binds to another. One of the most important forces involved in stabilizing these interactions is the electrostatic force. This project on implanting charges within proteins should lead to a better understanding of the electrostatic force and so should help improve these methodologies.