Murciano-Calles Javier, Coello Andrea, Cámara-Artigas Ana, Martinez Jose C
Department of Physical Chemistry and Institute of Biotechnology, Faculty of Sciences, University of Granada, Granada, Spain.
Department of Chemistry and Physics, Agrifood Campus of International Excellence (ceiA3), Research Centre for Mediterranean Intensive Agriculture and Food Biotechnology (CIAMBITAL), University of Almería, Almería, Spain.
J Mol Recognit. 2020 Apr;33(4):e2826. doi: 10.1002/jmr.2826. Epub 2019 Nov 19.
N-Methyl-D-aspartate (NMDA) receptors are key components in synaptic communication and are highly relevant in central nervous disorders, where they trigger excessive calcium entry into the neuronal cells causing harmful overproduction of nitric oxide by the neuronal nitric oxide synthase (nNOS) protein. Remarkably, NMDA receptor activation is aided by a second protein, postsynaptic density of 95 kDa (PSD95), forming the ternary protein complex NMDA/PSD95/nNOS. To minimize the potential side effects derived from blocking this ternary complex or either of its protein components, a promising approach points to the disruption of the PSD-95/nNOS interaction which is mediated by a PDZ/PDZ domain complex. Since the rational development of molecules targeting such protein-protein interaction relies on energetic and structural information herein, we include a thermodynamic and structural analysis of the PSD95-PDZ2/nNOS-PDZ. Two energetically relevant events are structurally linked to a "two-faced" or two areas of recognition between both domains. First, the assembly of a four-stranded antiparallel β-sheet between the β hairpins of nNOS and of PSD95-PDZ2, mainly enthalpic in nature, contributes 80% to the affinity. Second, binding is entropically reinforced by the hydrophobic interaction between side chains of the same nNOS β-hairpin with the side chains of α2-helix at the binding site of PSD95-PDZ2, contributing the remaining 20% of the total affinity. These results suggest strategies for the future rational design of molecules able to disrupt this complex and constitute the first exhaustive thermodynamic analysis of a PDZ/PDZ interaction.
N-甲基-D-天冬氨酸（NMDA）受体是突触通讯的关键组成部分，在中枢神经系统疾病中高度相关，在这些疾病中，它们会引发过量的钙进入神经元细胞，导致神经元型一氧化氮合酶（nNOS）蛋白产生有害的过量一氧化氮。值得注意的是，NMDA受体的激活由第二种蛋白质——95 kDa的突触后致密蛋白（PSD95）辅助，形成三元蛋白复合物NMDA/PSD95/nNOS。为了尽量减少因阻断这种三元复合物或其任何一种蛋白质成分而产生的潜在副作用，一种有前景的方法是破坏由PDZ/PDZ结构域复合物介导的PSD-95/nNOS相互作用。由于针对这种蛋白质-蛋白质相互作用的分子的合理开发依赖于此处的能量和结构信息，我们对PSD95-PDZ2/nNOS-PDZ进行了热力学和结构分析。两个与能量相关的事件在结构上与两个结构域之间的“双面”或两个识别区域相关联。首先，nNOS和PSD95-PDZ2的β发夹之间形成了一个四链反平行β折叠，主要是焓性质的，对亲和力的贡献为80%。其次，相同的nNOSβ发夹侧链与PSD95-PDZ2结合位点处α2螺旋侧链之间的疏水相互作用在熵上增强了结合，对总亲和力的贡献为剩余的20%。这些结果为未来合理设计能够破坏这种复合物的分子提供了策略，并构成了对PDZ/PDZ相互作用的首次详尽热力学分析。
