κ阿片受体三维结构的模建及其与强啡肽A(1-8)作用机制的研究(英文)

目的:模建人Kappa阿片受体(HKOR)三维结构,并研究它与强啡肽A(1-8)(Dyn8)的相互作用机制。方法:以牛视紫红质(OPSD)为模板,运用比较分子模拟模建HKOR七段跨膜区的三维结构。运用分子动力学优化HKOR模型并根据强啡肽A(1-14)核磁共振结果构建其三维结构,通过自建数据库搜寻建立HKOR的膜外环区。应用DOCK4.0将强啡肽A(1-8)与HKOR进行对接。结果:(1)得到HKOR三维模型,并用理论及实验参数进行了校正。(2)合理解释了Dyn8-HKOR相互作用机制:Asp138通过与Dyn8的N端残基形成氢键及静电作用,在配体受体结合过程中起着重要的作用。(3)HKOR膜外第二环区(EL2)中带负电荷的氨基酸Asp223和Glu209与Dyn8的C端带正电荷的残基相互作用,而Glu209可能是决定肽类配体特异性的一个重要因素。结论:EL2,TM3,TM4,TM5上的一些关键氨基酸残基决定Kappa阿片受体与肽类配体的选择性结合。     

孤啡肽和阿片类配体与阿片孤儿受体相互作用的机制研究(英文)

目的:研究孤啡肽和阿片类配体与阿片孤儿受体相 互作用的分子机制。方法:用分子动力学方法计算孤啡肽的最低能构象;通过分子对接程序将孤啡肽、阿片类配体对接到阿片孤儿受体的结合口袋中;通过结合能的计算研究配体对受体的亲和力与它们的结合能之间的关系。结果:孤啡肽(1-4)残基位于结合口袋的底部,孤啡肽(5-7)残基位于结合口袋的顶部,孤啡肽(8-17)残基与孤儿受体的第二膜外环区结合;阿片类配体和孤儿受体的结合方式与孤啡肽的情况类似,区别在于孤儿受体参与配体结合的残基种类和数量不同,因而亲和力不同;配体-受体的结合能与配体的亲和力之间有很好的相关性;预测了洛芬太尼四个异构体与阿片孤儿受体的亲和力。结论:该研究能够解释许多实验事实,有助于进一步理解阿片受体与配体相互作用的分子机制并设计新的分子生物学实验。     

HIV-共受体CCR5的三维结构及与其拮抗剂TAK 779相互作用的比较分子模拟(英文)

目的:研究HIV-1的共受体CCR5与其拮抗剂TAK779的相互作用机制。方法:用比较分子模拟方法建立CCR5受体的三维结构模型;通过量子化学计算得到TAK779分子的结构参数和最优几何构型;用DOCK4.0程序将TAJ779分子对接到CCR5受体的结合位点上。结果:通过分子力学优化得到了CCR5受体的三维结构模型,配体的结合口袋位于第三、五、六、七跨膜区,组成结合口袋的氨基酸残基主要为Thr105、Leu107、Tyr108、Gly111、Phe112、Ser114、Gly115、Lys197、Glu283、Gly286、Met287、Cys290;TAK779与CCR5受体的相互作用方式为氢键、静电和疏水作用;配体与受体的结合能为-51.606 kcal/mol。结论:上述模型有助于进一步理解膜受体识别HIV-1病毒的分子机制并设计新的HIV-1抑制剂。     

δ阿片受体研究新进展

目的综述δ阿片受体研究进展。方法应用功能表达、受体结合、基因定位突变、构建嵌合受体等方法。结果和结论克隆出δ阿片受体,为３７２个氨基酸,属Ｇ蛋白耦联受体,存在７次跨膜结构。δ阿片受体中的天门冬氨酸９５（Ａｓｐ９５）残基和Ａｓｐ１２８残基处于受体结合位点的关键区域。δ阿片受体中的赖氨酸（Ｌｙｓ１０８）残基阻止ＤＡＭＧＯ与δ受体的结合;δ阿片受体的第３个细胞外环决定了δ受体激动剂对δ受体的选择性。δ受体第４跨膜域中的丝氨酸（Ｓｅｒ１７７）被突变可使经典拮抗剂呈现激动剂的性质。     

Molecular modeling on kappa opioid receptor and its interaction with nonpeptide kappa opioid agonists 1

目的：研究κ阿片受体及其与非肽类激动剂的作用机制．方法：以细菌视紫红质为模板,模建κ阿片受体七个跨膜区的三维结构;将五个高活性非肽类激动剂对接到螺旋区内,研究作用机制．结果：（１）四氢吡咯环氮原子与Ａｓｐ１３８羧基成氢键;（２）乙酰胺羰基氧与受体Ｓｅｒ１８７间存在氢键作用;（３）与乙酰胺相连的疏水基团处于由Ｖａｌ２３９、Ｖａｌ２３６、Ｐｈｅ２３５、Ｖａｌ２３２、Ｌｅｕ１８６和Ｔｒｐ１８３构成的疏水区域内;（４）激动剂的四氢吡咯环为Ｉｌｅ２９０、Ａｓｐ１３８、Ｉｌｅ１９４、Ｉｌｅ１３５和Ｃｙｓ１３１残基包围．结论：模型将有助于设计新型高效安全的κ阿片受体激动剂．     

κ阿片受体分子模拟及其与非肽类κ阿片激动剂的作用

目的：研究了κ阿片受体及其与非肽类激动剂的作用机制。方法;以细菌视紫红质为模板,模建κ阿片受体七个跨膜区的三维结构,将五个高活性非肽类激动剂对接以螺旋区内,研究作用机制。结果：（１）四氢吡咯环氮原子与Ａｓｐ１３８羧基成氢键;（２）乙酰胺羰基氧与受体Ｓｅｒ１８７间存在在氢键作用;（３）与乙酰胺相连的疏水基团处于由Ｖａｌ２３９,Ｖａｌ１２３６,Ｐｈｅ２３５,Ｖａｌ２３２,Ｌｅｕ１８６和Ｔｒｐ１８３构成     

μ阿片受体及其与羧甲芬太尼相互作用的分子模拟

建立μ阿片受体的结构模型，并结合模型研究羧甲芬太尼对该受体的作用机制。以细菌视紫红质的三维结构为模板，在计算机上建立μ阿片受体模型，然后将羟甲芬太尼对接到假想的受体结合部位。得到了良好的配体－受体相互作用模型，发现残基Ａｓｐ１４７与Ｈｉｓ３１９为可能的结合位点。     

阿片受体及阿片肽研究进展

阿片受体属G蛋白偶联受体,该类受体具有相同的基本结构:一个细胞外氨基端区域,7个跨膜域以及一个细胞内羟基端尾区.     

多巴胺D2胺体三维结构预测及与激动剂配体相互作用的研究

以细菌视紫红质（bacteriorhodopsin）的三维晶体结构为模板，预测了多巴胺D2受体跨膜区的七个α螺旋肽段的三维结构。根据定点突变实验数据以及预测的受体三维结构，确定了激动剂配体结合胺由Asp86,Ser141,Ser144等十十个氨基酸残基组成。为了校正和检验所得的模型，分别以一组刚性、一组柔性的激动剂与受体对接（DOCK），分析－logIC50和结合能Eb相关性，较好的结果说明该模型是可靠的。     

Modeling of Dopamine D2 Receptor and its Agonist DOCK Analyses

以细菌视紫红质（ｂａｃｔｅｒｉｏｒｈｏｄｏｐｓｉｎ）的三维晶体结构为模板，预测了多巴胺Ｄ２受体跨膜区的七个α螺旋肽段的三维结构。根据定点突变实验数据以及预测的受体三维结构，确定了激动剂配体结合腔由Ａｓｐ８６，Ｓｅｒ１４１，Ｓｅｒ１４４等十二个氨基酸残基组成。为了校正和检验所得的模型，分别以一组刚性、一组柔性的激动剂与受体对接（ＤＯＣＫ），分析ｌｏｇＩＣ５０和结合能Ｅｂ相关性，较好的结果说明该模型是可靠的     

Opioid receptor-like 1 (ORL1) molecular "road map" to understanding ligand interaction and selectivity

The opioid receptor-like 1 (ORL1) system has attracted a lot of attention owing to its diverse physiological role and by its close structural proximity toward the classical opioid receptors. Even though they share a close sequence similarity, the ligand recognition pattern for the ORL1 receptor and the classical opioid receptors remains highly distinct. In addition, functional diversification observed between the ORL1 receptor system and classical opioid receptors clearly indicates that subtle changes in the structural makeup of a receptor are enough to delineate them. A clear understanding of the structural requirements for ligand selectivity by classical opioid receptors and identification of a common "opioid binding pocket" has not been achieved yet. At this juncture, the ORL1 receptor system presents itself as a potential tool in the quest for elucidating critical elements directing ligand selectivity. The current paper is a compilation of several site-directed mutagenesis studies conducted on the ORL1 receptor system. The mutagenesis studies concentrated on the transmembrane domain residues are reported with the changes observed in terms of both binding and functional activation of the receptor. Given the critical role played by this G-protein coupled receptor, molecular level understanding of this ORL1 receptor system would aid in rational design and development of agonists and antagonists with multiple therapeutic applications.     

Investigation of the selectivity of oxymorphone- and naltrexone-derived ligands via site-directed mutagenesis of opioid receptors: exploring the "address" recognition locus

The delta-selective opioid antagonist naltrindole (NTI), as well as the kappa-selective opioid antagonists norbinaltorphimine (norBNI) and 5'-guanidinonaltrindole (GNTI), are derived from naltrexone, a universal opioid antagonist. Previous studies have indicated that extracellular loop III is the key region for discrimination by naltrexone-derived selective ligands between the delta, mu, and kappa opioid receptor types. It has been proposed that selective ligands could bind to all three receptor types if the appropriate portions of the extracellular loops were eliminated. To investigate this possibility, several single-point mutant opioid receptors have been generated with the aim of conferring enhanced affinity of selective ligands for their nonpreferred receptor types. Mutations were made in all three types of opioid receptors with the focus on two positions at the extracellular end of transmembrane regions (TM) VI and VII. It was found that the delta-selective NTI could bind both mu and kappa receptors with significantly enhanced affinity when an aromatic residue in TM VII was replaced with alanine (mu[W318A] and kappa[Y312A]). Similarly, kappa-selective antagonists, norBNI and GNTI, showed enhanced affinity for the mu[W318A] mutant and for both mu and delta receptors when a glutamate residue was incorporated into the extracellular end of TM VI (mu[K303E] and delta[W284E]). These results demonstrate that naltrexone-derived selective ligands achieve their selectivity via a combination of enhanced affinity of the address for a particular subsite along with loss of affinity due to steric interference at nonpreferred types. The results reveal key residues in the "address" recognition locus that contribute to the selectivity of opioid ligands and support the hypothesis that recognition of the naltrexone moiety is essentially the same for all three receptor types.     

Endomorphin-1 discriminates the mu-opioid receptor from the delta- and kappa-opioid receptors by recognizing the difference in multiple regions

Endomorphin-1 is a novel endogenous peptide that is highly selective for the mu-opioid receptor over the delta- and kappa-opioid receptors. The structural basis of high selectivity of endomorphin-1 to the mu-opioid receptor was examined using chimeric receptors between mu- and delta-opioid receptors and those between mu- and kappa-opioid receptors. The chimeric receptors were constructed by using restriction enzyme sites intrinsically possessed by or introduced to the mu-, delta- and kappa-opioid receptor cDNAs. The junctions for the construction were located at the first intracellular loop (Bbs I site), third transmembrane domain (Afl III site) and fifth transmembrane domain (Bgl II site). The competitive binding assay using chimeric receptors revealed that the region from the Bbs I site to the Afl III site, including the first extracellular loop, contributes to the discrimination between mu- and delta-opioid receptors by endomorphin-1 more than any other regions. However, the region from the Afl III site to the Bgl II site and that from the Bgl II site to the carboxy terminal also somewhat contribute to the discrimination between mu- and delta-opioid receptors. For the discrimination between mu- and kappa-opioid receptors, two regions, that is, the region from the Bbs I site to the Afl III site and that from the Bgl II site to the carboxy terminal, were shown to be important. The present results show that endomorphin-1 discriminates the mu-opioid receptor from the other two types of opioid receptors by recognizing the differences in several amino acid residues widely distributed through the receptor structure. We previously reported that DAMGO, a synthetic highly mu-selective peptide, discriminates between mu- and delta-opioid receptors by recognizing the difference in only one amino acid residue and discriminates between mu- and kappa-opioid receptors by recognizing the difference in four residues localized in the restricted region. Although both endomorphin-1 and DAMGO are mu-opioid receptor selective peptides, molecular mechanisms for mu-selectivity are different between these peptides.     

Structures of the intradiskal loops and amino terminus of the G‐protein receptor,rhodopsin

Abstract: The intradiskal surface of the transmembrane protein, rhodopsin, consists of the amino terminal domain and three loops connecting six of the seven transmembrane helices. This surface corresponds to the extracellular surface of otherG‐protein receptors. Peptides that represent each of the extramembraneous domains on this surface (three loops and the amino terminus) were synthesized. These peptides also included residues which, based on a hydrophobic plot, could be expected to be part of the transmembrane helix. The structure of each of these peptides in solution was then determined using two‐dimensional ¹H nuclear magnetic resonance. All peptide domains showed ordered structures in solution. The structures of each of the peptides from intradiskal loops of rhodopsin exhibited a turn in the central region of the peptide. The ends of the peptides show an unwinding of the transmembrane helices to form this turn. The amino terminal domain peptide exhibitedα‐helical regions with breaks and bends at proline residues. This region forms a compact domain. Together, the structures for the loop and amino terminus domains indicate that the intradiskal surface of rhodopsin is ordered. These data further suggest a structural motif for short loops in transmembrane proteins. The ordered structures of these loops, in the absence of the transmembrane helices, indicate that the primary sequences of these loops are sufficient to code for the turn.     

Opioid activity profiles indicate similarities between the nociceptin/orphanin FQ and opioid receptors

Nociceptin (orphanin FQ) is the recently discovered peptide agonist for the orphan receptor opioid receptor-like 1 (ORL1). Despite the high sequence homology between ORL1 and the opioid receptors, most opioids lack affinity for the nociceptin receptor. The affinity and functional profile of opioids possessing activity at the nociceptin receptor was determined using [3H]nociceptin and nociceptin-stimulated [35S]GTPgammaS binding. The mu-opioid receptor-selective agonist lofentanil potently and competitively displaced [3H]nociceptin at rat brain receptors (IC(50) 62 nM). Lofentanil exhibited full agonism for enhancement of [35S]GTPgammaS binding to human recombinant ORL1 receptors (EC(50) 50 nM). The related piperidines ohmefentanyl and sufentanil and the nonselective opioid receptor agonist etorphine were less potent nociceptin receptor agonists. The kappa(1)+kappa(3)-opioid receptor agonist/mu-opioid receptor antagonist naloxone benzoylhydrazone was a pure antagonist at both rat brain and human ORL1 receptors. The nonselective opioid receptor partial agonist buprenorphine and the nonselective opioid receptor antagonist (-)-quadazocine exhibited pure antagonism at rat brain receptors, but displayed partial agonism at human ORL1 receptors. Thus, opioids displaying full agonism at the nociceptin receptor are also opioid receptor agonists, whereas opioids that are antagonists or partial agonists at the nociceptin receptor show antagonism or partial agonism at opioid receptors. In addition, the stereospecificity required at opioid receptors appears to be retained at the nociceptin receptor, since (+)-quadazocine is inactive at both receptors. These findings illustrate the structural and functional homology of the opioid recognition site on these two receptor classes and suggest that opioids may provide leads for the design of nonpeptide nociceptin receptor agonists and antagonists lacking affinity for the classical opioid receptors.     

Building 3D-structural model of kappa opioid receptor and studying its interaction mechanism with dynorphin A(1-8)

AIM: To construct the 3D-structural model of human kappa opioid receptor (HKOR) and study its interacting mechanism with dynorphin A(1-8) (Dyn8). METHODS: Comparative molecular modeling was applied to build the 7 transmembrane (TM) helical domain of HKOR using the bovine rhodopsin (OPSD) model as a template. Molecular dynamics was performed to minimize the HKOR model and to simulate the 3D-structure of Dyn8 based on the NMR results of dynorphin A(1-14). The extracellular loops (EL) were built by self-constructed database searching. DOCK4.0 program was performed to construct Dyn8 complex with HKOR. RESULTS: (1) The model of HKOR was obtained and validated by theoretical and experimental data. (2) The Dyn8-HKOR interacting mechanism is reasonably explained: Side chain of residue Asp138 interacts with protonated nitrogen atom at the N-terminal residues of Dyn8 through electrostatic and hydrogen bonding, which play an important role in ligand binding with receptor. (3) Negatively charged amino acids in the second extracellular loop (EL2) as Asp223 and Glu209 interact with the C-terminal positively charged residues in Dyn8, and Glu209 is a likely determinant of peptide ligand specificity. CONCLUSION: Some amino acid residues positioned in EL2, TM3, TM4, and TM5 form the binding site and therefore determine the selectivity of kappa peptide agonist.     

Functional inactivation of the nociceptin receptor by alanine substitution of glutamine 286 at the C terminus of transmembrane segment VI: evidence from a site-directed mutagenesis study of the ORL1 receptor transmembrane-binding domain

A site-directed mutagenesis approach has been used to gain insight into the molecular events whereby the heptadecapeptide nociceptin binds and activates the opioid receptor-like 1 (ORL1) receptor, a G protein-coupled receptor. Alanine mutation, in the human ORL1 receptor, of transmembrane amino acid residues that are conserved in opioid receptors, Asp(130) and Tyr(131) in transmembrane segment (TM) III, Phe(220) and Phe(224) in TM V, and Trp(276) in TM VI, yields mutant receptors with reduced affinity, and proportionally decreased reactivity, toward nociceptin. Least to most deleterious in this respect are Ala substitutions of Phe(220) approximately W276A < Tyr(131) < Phe(224) 10,000 nM compared with 0.8 nM at the wild-type receptor). In all respects, this mutant receptor appears to be functionally inactive, indicating that residue Gln(286) may play a pivotal role in ORL1 receptor-mediated transduction of the nociceptin signal.     

人CCR5受体与CD4抗原和HIV-1包膜糖蛋白gp120复合物的分子模型(英文)

目的:研究人CCR5与CD4抗原和HIV-1包膜糖蛋白gp120的相互作用。方法:人CCR5受体的结构保守区由SYBYL软件中的Biopolymer模块建立,非保守区由LOOP SEARCH方法建立。将得到的结构模型与CD4抗原和gp120结合形成复合物。结果:人CCR5受体既可以与CD4抗原相互作用,也可以和gp120相互作用,其N-末端残基通过静电和氢键方式与CD4相互作用,并深埋在一个疏水中心里,被碱性基团包围。而且有7个氨基酸残基通过范德华作用、疏水性作用和氢键与6个gp120残基相互作用。结论:该模型将有助于设计作用更强的抗艾滋病药物。