Jackson Shelley N, Wang Hay-Yan J, Yergey Alfred, Woods Amina S
NIDA IRP, NIH, 5500 Nathan Shock Drive, Baltimore, Maryland 21224, USA.
J Proteome Res. 2006 Jan;5(1):122-6. doi: 10.1021/pr0503578.
Receptor heteromerization is an important phenomenon that results from the interaction of epitopes on two receptors. Previous studies have suggested the possibility of Dopamine D2-NMDA receptors' interaction. We believe that the interaction is through an acidic epitope of the NMDA NR1 subunit (KVNSEEEEEDA) and a basic epitope of the D2 third intracellular loop (VLRRRRKRVN), which was shown to also interact with the Adenosine A2A receptor. In previous work, we highlighted the role of certain amino acid residues, mainly two or more adjacent arginine on one peptide and two or more adjacent glutamate, or aspartate, or a phosphorylated residue on the other in the formation of noncovalent complexes (NCX) between epitopes. In the present work, we use the phosphorylated (KVNSpEEEEEDA), nonphosphorylated (KVNSEEEEEDA) and modified (KVNpSAAAAAAA) forms of the NMDA epitope that possibly interact with the D2 epitope to investigate the gas-phase stability of the NCXs as a function of the nominal energy given to the NCX ion as it enters the collision cell. In addition to theoretical calculations, the experimental data was used to calculate the stability of each electrostatic complex versus that of the dimer of KVNSpEEEEEDA. Our results demonstrate the importance of the phosphate group in stabilizing molecular interactions and that appreciably higher collision energies are required to completely dissociate any of the three different NCX ions that are formed through electrostatic interaction in comparison to the energy required to dissociate the KVNpSEEEEEDA dimer ion, which is mainly kept together by hydrogen bonding. This study emphasizes ionic bonds stability and their importance to protein structure as their potent electrostatic attractions can in the gas-phase surpass the strength of covalent bonds.
受体异聚化是一种重要现象，它源于两个受体上抗原决定簇之间的相互作用。先前的研究表明多巴胺D2-NMDA受体存在相互作用的可能性。我们认为这种相互作用是通过NMDA NR1亚基的酸性抗原决定簇（KVNSEEEEEDA）和D2第三细胞内环的碱性抗原决定簇（VLRRRRKRVN）实现的，后者也被证明可与腺苷A2A受体相互作用。在先前的工作中，我们强调了某些氨基酸残基的作用，主要是一条肽链上两个或更多相邻的精氨酸以及另一条肽链上两个或更多相邻的谷氨酸、天冬氨酸或一个磷酸化残基，它们在抗原决定簇之间形成非共价复合物（NCX）中发挥作用。在本研究中，我们使用可能与D2抗原决定簇相互作用的NMDA抗原决定簇的磷酸化形式（KVNSpEEEEEDA）、非磷酸化形式（KVNSEEEEEDA）和修饰形式（KVNpSAAAAAAA），来研究NCXs的气相稳定性与NCX离子进入碰撞池时所赋予的标称能量之间的函数关系。除了理论计算外，实验数据还用于计算每种静电复合物相对于KVNSpEEEEEDA二聚体的稳定性。我们的结果表明磷酸基团在稳定分子相互作用中的重要性，并且与解离主要通过氢键结合在一起的KVNpSEEEEEDA二聚体离子所需的能量相比，要完全解离通过静电相互作用形成的三种不同NCX离子中的任何一种，都需要明显更高的碰撞能量。这项研究强调了离子键的稳定性及其对蛋白质结构的重要性，因为它们强大的静电吸引力在气相中可能超过共价键的强度。
