STRUCTURE DETERMINATION OF ION CHANNEL PROTEINS

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 OmpF孔蛋白是在革兰氏阴性菌的外膜（OM）中发现的阳离子选择性水通道。 它们的主要功能是促进小的亲水性溶质穿过OM的易位。 OmpF孔蛋白的一个独特特征是细胞外环折叠到孔的内部，产生收缩区。 有人建议，在收缩区的电荷不对称性可能会引起一个强大的电场，并有助于渗透的偶极溶质。 计算研究表明，OmpF具有有趣的离子传导特性，其中阳离子和阴离子遵循分离的路径。 然而，这一特征尚未在实验中直接观察到。 因此，我们采用X射线晶体学，以研究阳离子和阴离子的选择性途径沿着OmpF孔。 除了其独特的离子传导特性外，OmpF通道也是允许抗生素分子渗透革兰氏阴性细菌细胞的主要通道。 随着抗生素耐药性的出现，由于膜通透性降低，有必要找到增加抗生素转运穿过OmpF孔蛋白的方法。 因此，在第二子项目中，我们将OmpF与各种抗生素复合结晶。 这是第一次，我们能够在分子水平上实验性地可视化蛋白质-药物相互作用。 因此，这项工作的结果将提供见解的抗生素的设计与改进的扩散特性和目标特异性。离子型谷氨酸受体离子通道（iGluRs）介导大脑和脊髓中绝大多数突触的兴奋性反应。神经递质分子与这些受体的配体结合结构域（LBD）的结合驱动跨膜孔的打开。 这些受体组装成四聚体。 然而，以前的晶体结构只揭示了二聚体复合物。 因此，在这第三个项目中，我们已经解决了一种新型GluR 2 LBD二聚体的晶体结构。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. OmpF porins are cation-selective aqueous channels found in the outer membrane (OM) of Gram-negative bacteria. Their main function is to facilitate the translocation of small hydrophilic solutes across the OM. One unique feature of the OmpF porin is an extracellular loop that folds into the interior of the pore, creating the constriction zone. It has been suggested that charge asymmetry in the constriction zone could give rise to a strong electric field and aid in permeation of dipolar solutes. Computational studies have suggested an intriguing ion-conducting property of OmpF, in which cations and anions follow separated pathways. However, this feature has yet to be directly observed experimentally. We are, therefore, employing x-ray crystallography in order to study the cation and anion selective pathways along the OmpF pore. In addition to its unique ion conduction properties, the OmpF channel is also the main gateway that allows antibiotic molecules to permeate Gram-negative bacterial cells. With the emergence of antibiotic resistance by virtue of decreased membrane permeability, it is necessary to find ways to increase antibiotic translocation across OmpF porin. Therefore, in a second subproject, we have crystallized OmpF in complex with various antibiotics. For the first time, we are able to experimentally visualize protein-drug interactions at the molecular level. Therefore, results of this work will give insights into the design of antibiotics with improved diffusional characteristics and target specificity. The ionotropic glutamate receptor ion channels (iGluRs) mediate excitatory responses at the vast majority of synapses in the brain and spinal cord. The binding of neurotransmitter molecules to the ligand-binding domain (LBD) of these receptors drives the opening of the transmembrane pore. These receptors assemble as tetramers. However, previous crystal structures have revealed only dimer complexes. Therefore, in this third project, we have solved the crystal structure of a novel GluR2 LBD dimer-of-dimers.