Chemical structures and biological activities of non-peptide selective kappa opioid ligands.
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Humans↗
Biomedical subjects
D C Rees
Publications and source records attributed to D C Rees.
Forces involved in the assembly and stabilization of membrane proteins.
Hydrophobic organization: Determination of the structure of the bacterial photosynthetic reaction center, bacterial porins, and bacteriorhodopsin allows a comparison of the basic structural features of integral membrane proteins. Structure parameters of membrane- and water-soluble proteins are surprisingly similar, given the different dielectric environments, except for the polarity of residues on the protein surface. Hydrophobic and electrostatic forces: 1) Intramembrane helix-helix interactions that are sensitive to small structure changes can dictate assembly of membrane proteins, as indicated by reconstitution of bacteriorhodopsin from proteolytic fragments and specific dimer formation of the human erythrocyte sialoglycoprotein glycophorin A. 2) Electrostatic interactions have an important role in determining the trans-membrane orientation of integral membrane proteins of the bacterial inner membrane, as expressed by the "positive-inside" rule for the distribution of basic residues on the cis relative to the trans side of the membrane-spanning alpha-helices. The use of this charge asymmetry rule, in conjunction with a hydrophobicity algorithm for prediction of membrane-spanning domains, allows accurate prediction of the folding patterns of such polypeptides across the membrane. A role of electrostatic interactions in assembly and maintenance of the structure of oligomeric integral membrane protein complexes is also implied by the separation and extrusion from the membrane, at high pH, of the major hydrophobic subunits of the cytochrome b6f complex from the chloroplast thylakoid membrane. It is inferred that the hydrophobic helix-helix interactions between the subunits of this complex, whose function is electron transfer and proton translocation, are relatively weak compared to those in bacteriorhodopsin.
Crystallization↗
Three-dimensional structures of acidic and basic fibroblast growth factors.
Members of the fibroblast growth factor (FGF) family of proteins stimulate the proliferation and differentiation of a variety of cell types through receptor-mediated pathways. The three-dimensional structures of two members of this family, bovine acidic FGF and human basic FGF, have been crystallographically determined. These structures contain 12 antiparallel beta strands organized into a folding pattern with approximate threefold internal symmetry. Topologically equivalent folds have been previously observed for soybean trypsin inhibitor and interleukins-1 beta and -1 alpha. The locations of sequences implicated in receptor and heparin binding by FGF are presented. These sites include beta-sheet strand 10, which is adjacent to the site of an extended sequence insertion in several oncogene proteins of the FGF family, and which shows sequence conservation among the FGF family and interleukin-1 beta.
Amino Acid Sequence↗
Perspectives on non-heme iron protein chemistry.
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Amino Acid Sequence↗
Highly selective kappa opioid analgesics. 4. Synthesis of some conformationally restricted naphthalene derivatives with high receptor affinity and selectivity.
This paper describes the synthesis and kappa and mu opioid receptor binding affinity of some conformationally restrained derivatives of the arylacetamide group in the selective kappa opioid receptor agonist (+/-)-trans-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl]benzo [b]thiophene-4-acetamide monohydrochloride (1,PD117302), which is an analogue of U-50, 488. The methyl-substituted derivatives (+/-)-trans-N, alpha-dimethyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzo-[b] thiophene-4-acetamide monohydrochloride (6a,b) possess significantly weaker affinity than 1 for the kappa opioid receptor (Ki = 172 and 3.7 nM, respectively). It is proposed that this is due to the conformational restriction imposed by the methyl group of 6. In order to test this proposal the acenaphthene derivative and the 4,5-dihydro-3H-naphtho [1,8-bc]thiophene derivative were prepared. The acenaphthene derivative (+)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro [4.5]dec-8-yl]acenaphthenecarboxamide monohydrochloride (9) was found to have high kappa opioid receptor affinity and selectivity (kappa Ki = 0.37 +/- 0.05 nM, mu/kappa = 659, delta/kappa = 1562) and is 100 times more potent than morphine as an analgesic in the rat paw pressure test for analgesia after intravenous administration (MPE50 = 0.014 and 1.4 mg/kg, respectively). The 4,5-dihydro-3H-naphtho[1,8-bc]thiophene derivative (-)-4,5-dihydro-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro [4.5]dec-8-yl]-3H-naphthol[1,8-bc]thiophene-5-carboxamide p-toluenesulfonate (17) also has high kappa opioid receptor affinity and selectivity (kappa Ki = 4.65 nM, mu/kappa = 109).
Analgesics↗
An envelope-based approach for direct phase determination of macromolecular structures.
An initial electron density distribution for a crystal structure may be directly derived from observed diffraction data by maximizing the product of the observed and calculated Patterson functions with respect to the electron density values within an envelope. This maximization problem may be formulated as an eigenvalue equation, in which potential electron density distributions are obtained as eigendensities (eigenvectors) of a symmetric matrix. Elements of this matrix depend only on the indices and intensities of the observed reflections, and on the coordinates of grid points inside the envelope. Eigendensities are calculated for a set of small envelopes (enclosing about 20% of the molecular volume) covering a unique region of the unit cell whose points are unrelated by space-group operations, origin shifts or changes in enantiomorph. On the basis of correlation coefficients between the observed and calculated values for both the Patterson function and structure-factor amplitudes, a small set of eigendensities are selected for combination into a final electron density distribution. This electron density distribution may be Fourier transformed to yield calculated structure factors. Test calculations on lysozyme indicate that phase errors of less than 60 degrees may be obtained for strong low-resolution reflections by this procedure. An extension of this approach to handle crystal structures containing non-crystallographic symmetry is described.
Chemical Phenomena↗
Highly selective kappa-opioid analgesics. 3. Synthesis and structure-activity relationships of novel N-[2-(1-pyrrolidinyl)-4- or -5-substituted-cyclohexyl]arylacetamide derivatives.
This paper describes the chemical synthesis, mu/kappa opioid receptor selectivity and analgesic activity of 14 novel N-[2-(1-pyrrolidinyl)-4- or -5-substituted-cyclohexyl]arylacetamide derivatives. The prototype kappa-selective agonist, PD117302 (trans-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzo[b]thiophene-4- acetamide, 2) has been regio- and stereoselectively substituted in the C-4 and C-5 positions of the cyclohexyl ring with the methyl ether and spiro tetrahydrofuran groups. It is observed that optimal mu/kappa-receptor selectivity is obtained when the oxygen atom of the methyl ether or the tetrahydrofuran ring is joined to the equatorial C-4 position. Hence, (-)-(5 beta,7 beta,8 alpha)-N-methyl-N-[7-(1-pyrrolidinyl)-1- oxaspiro[4.5]dec-8-yl]benzo[b]furan-4-acetamide monohydrochloride (21) has exceptionally high kappa opioid receptor affinity and selectivity in vitro (kappa Ki = 0.83 nM, mu/kappa ratio = 1520) is the most potent kappa-selective analgesic ever reported. Compound 21 is 25 times more potent than morphine and 17 times more potent than U-62066 (spiradoline, 19) when assayed by the rat paw pressure test by intravenous administration (MPE50 = 0.024, 0.6, and 0.4 mg/kg, respectively).
Analgesia↗
CI-977, a novel and selective agonist for the kappa-opioid receptor.
1. CI-977 is a new, nonpeptide kappa-opioid compound that has been synthesized and its pharmacological properties determined in a series of in vitro and in vivo rodent models. 2. In a radioligand binding studies, with guinea-pig forebrain homogenates, CI-977 bound with high affinity to [3H]-U69593-labelled kappa-sites (Ki = 0.11 nM) but with low affinity to [3H]-[D-Ala2, MePhe4, Gly-ol5] enkephalin (DAMGO) labelled mu-sites (Ki = 99 nM) and [3H]-[D-Pen2.5]enkephalin (DPDPE) labelled delta-sites (Ki = 1.04 microM). CI-977 also bound with negligible affinity to [3H]-(+)-3-(1-propyl-3-piperi-dinyl)phenol (3-PPP) labelled sigma-sites (Ki = 1.9 microM) and [3H]-1-(1-[2-thienyl]cyclohexyl)piperidine (TCP) labelled PCP sites (Ki greater than 10 microM). 3. CI-977 produced a potent inhibition of the electrically-evoked contractions of the guinea-pig ileum and rabbit vas deferens with IC50 values of 0.087 nM and 3.3 nM, respectively. The pKB values for the opioid antagonists naloxone (7.6) and norbinaltorphimine (10.5) supported the kappa nature of the CI-977-mediated effects in the smooth muscle assays. 4. CI-977 was a potent antinociceptive agent against a mechanical noxious stimulus in rats following intravenous, intramuscular, subcutaneous and oral administration. CI-977 was also effective against mechanical and chemical noxious stimuli in the mouse but ineffective against a thermal stimulus. The antinociceptive effects produced by CI-977 were completely reversed by naloxone (1 mg kg-1, s.c.). 5. At doses close to those required to produce antinociception, CI-977 also caused a naloxone-reversible diuresis and inhibition of locomotor activity.6. The in vitro and in vivo pharmacological profile of CI-977 demonstrates that it is a potent and selective agonist at the Kappa-opioid receptor.
Analgesics↗
Qualitative and quantitative comparability of human and animal developmental neurotoxicants: a workshop summary.
A Workshop on the Qualitative and Quantitative Comparability of Human and Animal Developmental Neurotoxicity was held in Williamsburg, Va. on April 11-13, 1989. Based upon data presented at the Workshop, the degree of qualitative and quantitative comparability between data obtained from humans and experimental animals is reviewed for several developmental neurotoxicants (lead, agents of abuse, alcohol, PCBs, phenytoin, methylmercury, and ionizing radiation). Qualitative comparability was considered for the following functional categories: motor development and function, cognitive function, sensory function, motivation/arousal behavior, and social behavior. Quantitative comparability was assessed by comparing administered dose as well as measures of internal dose (e.g., blood levels) for selected agents. Comparability of qualitative changes between humans and rodents was most apparent when comparisons were made on the basis of general categories of behavioral function. These data support the use of animal models in assessing risk for developmental neurotoxicants and provide guidance on the types of functional end points that can be incorporated into a developmental neurotoxicity testing battery. Evidence of quantitative comparability was most apparent when an internal measure of dose (e.g., blood level) was used.
Animals↗
Hydrophobic organization of membrane proteins.
Membrane-exposed residues are more hydrophobic than buried interior residues in the transmembrane regions of the photosynthetic reaction center from Rhodobacter sphaeroides. This hydrophobic organization is opposite to that of water-soluble proteins. The relative polarities of interior and surface residues of membrane and water soluble proteins are not simply reversed, however. The hydrophobicities of interior residues of both membrane and water-soluble proteins are comparable, whereas the bilayer-exposed residues of membrane proteins are more hydrophobic than the interior residues, and the aqueous-exposed residues of water-soluble proteins are more hydrophilic than the interior residues. A method of sequence analysis is described, based on the periodicity of residue replacement in homologous sequences, that extends conclusions derived from the known atomic structure of the reaction center to the more extensive database of putative transmembrane helical sequences.
Bacterial Proteins↗
Cross-linking of nitrogenase components. Structure and activity of the covalent complex.
The nitrogenase complex from Azotobacter vinelandii is composed of the MoFe protein (Av1), an alpha 2 beta 2 tetramer, and the Fe protein (Av2), a gamma 2 dimer. During turnover of the enzyme, electrons are transferred from Av2 to Av1 in parallel with the hydrolysis of MgATP. Using the cross-linking reagent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, we have identified some of the properties of the complex between the two components. The cross-linking reaction was highly specific yielding a single apparent Mr = 97,000 protein. The amount of cross-linked product was essentially independent of whether MgATP or MgADP were in the reaction. Also, the amount was maximum at high ratios of Av2 to Av1. The Mr = 97,000 protein was characterized by amino acid analysis and Edman degradation and was found to be consistent with a 1:1 complex of an Av2 gamma subunit and an Av1 beta subunit (the amino terminal serine subunit). The complex was no longer active in the nitrogenase reaction which supports, but does not prove, the requirement for dissociation of the complex after each electron transferred. Nitrogenase activity and cross-linking were inhibited in an identical way by NaCl, which suggests that electrostatic forces are critical to the formation of the electron transfer complex.
Amino Acids↗
Evidence of tolerance following repeated exposure to toluene in the rat.
Toluene shares pharmacological properties with other abused central nervous system depressants such as ethanol and the barbiturates. Although tolerance has been clearly demonstrated for these classic CNS depressants, evidence of tolerance following repeated toluene exposure is equivocal. The present work examined if tolerance would develop to the effects of repeated toluene exposure on learned behavior and examined the possibility that external discriminative stimuli could influence these effects. Two variants of a fixed-consecutive-number schedule of reinforcement were used as components in a multiple schedule. The components differed in whether or not behavior within them was under the control of external discriminative stimuli. Rats were exposed daily for two hours to toluene (1780 to 4500 ppm). Different patterns of effects emerged from repeated exposure; some rats displayed tolerance while the performance of others deteriorated. Behavior controlled by external discriminative stimuli was more resistant to disruption and showed tolerance more readily than did behavior not under such control.
Animals↗
Highly selective kappa-opioid analgesics. 2. Synthesis and structure-activity relationships of novel N-[(2-aminocyclohexyl)aryl]acetamide derivatives.
This paper describes the chemical synthesis and the development of structure-activity relationships (SAR) for the kappa opioid receptor affinity and mu/kappa opioid receptor selectivity of novel N-[(2-aminocyclohexyl)aryl]acetamide derivatives. The SAR of this series are investigated by consideration of structural modifications made to the aromatic moiety, the amide linkage, and cyclohexane and the pyrrolidine ring substituents of the prototype kappa selective agonist, PD117302 (trans-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzo[b]thiophene-4- acetamide) (1). The kappa and mu opioid receptor binding affinities of 23 novel compounds are reported. It is observed that optimal mu/kappa receptor selectivity is obtained with a benzo[b]thiophene aromatic system attached via the C-4 position, which is discussed in terms of steric and electronic parameters. The amide linkage has been replaced with the reversed amide, an ester, an aminomethylene, a thioamide, and a secondary amide. The best of these isosteres is the N-methyl amide. Substitution of the pyrrolidine ring of PD117302 in the 3-position with a hydroxymethylene group increases the mu/kappa selectivity compared to the unsubstituted compound, e.g. compound 14, trans-(+/-)-N-methyl-N-[2-[3-(hydroxymethyl)-1-pyrrolidinyl] cyclohexyl]-4-benzo[b]furanacetamide monohydrochloride, mu/kappa receptor selectivity = 244. The cis fused, 4,5 dimethyl ether substituted cyclohexane analogue trans-(+/-)-N-methyl-N-[4,5-dimethoxy-2-(1-pyrrolidinyl) cyclohexyl]-benzo[b]thiophene-4-acetamide monohydrochloride (32) has high in vitro kappa opioid receptor affinity (Ki = 16 nM) and equipotent analgesic activity to morphine after iv administration in rats.
Analgesics, Opioid↗
The bacterial photosynthetic reaction center as a model for membrane proteins.
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Amino Acid Sequence↗
Highly selective kappa opioid analgesics. Synthesis and structure-activity relationships of novel N-[(2-aminocyclohexyl)aryl]acetamide and N-[(2-aminocyclohexyl)aryloxy]acetamide derivatives.
This paper describes the synthesis, structure-activity relationships (SAR) of mu and kappa opioid binding affinities, and analgesic properties of a series of novel highly selective kappa opioid N-[(2-aminocyclohexyl)aryl]acetamide and N-[(2-aminocyclohexyl)aryloxy] acetamide derivatives. Ten compounds, 14, 15, 31-37, and 39 (Tables I and II), show a marked kappa selectivity of greater than 100:1 over mu binding, with high affinity for the kappa opioid receptor (approximately 10(-8) - 10(-9) M). Compound 39, (S,S-trans)-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-4-benzo[b] furanacetamide hydrobromide, has the highest mu/kappa selectivity, 780:1 (kappa Ki = 4.2 nM), reported to date. Four of these compounds, 14, 15, and their S,S-trans enantiomers, 37 and 39, respectively, produce effective analgesia by oral administration, as assayed by a rat-paw pressure test (RPP) (MPE50 = 24, 26, 8.3, and 12 mg/kg, respectively). The R,R-trans isomer, 38, was inactive in binding and RPP. The analgesic effect was reversed by administration of naloxone, confirming these effects are opioid in character. Optimal activity is produced when the basic nitrogen atom is in a pyrrolidine ring, the aryl group is a 10-pi-electron-rich aromatic system, such as 4-benzo[b]thiophene, 4-benzo[b]furan, or 4-chlorophenoxy, and overall lipophilicity lies within the range log P = 3.5-5.0.
Acetamides↗
Structure of the reaction center from Rhodobacter sphaeroides R-26 and 2.4.1: protein-cofactor (bacteriochlorophyll, bacteriopheophytin, and carotenoid) interactions.
The three-dimensional structures of the cofactors and protein subunits of the reaction center (RC) from the carotenoidless mutant strain of Rhodobacter sphaeroides R-26 and the wild-type strain 2.4.1 have been determined by x-ray diffraction to resolutions of 2.8 A and 3.0 A with R values of 24% and 26%, respectively. The bacteriochlorophyll dimer (D), bacteriochlorophyll monomers (B), and bacteriopheophytin monomers (phi) form two branches, A and B, that are approximately related by a twofold symmetry axis. The cofactors are located in hydrophobic environments formed by the L and M subunits. Differences in the cofactor-protein interactions between the A and B cofactors, as well as between the corresponding cofactors of Rb, sphaeroides and Rhodopseudomonas viridis [Michel, H., Epp, O. & Deisenhofer, J. (1986) EMBO J. 3, 2445-2451], are delineated. The roles of several structural features in the preferential electron transfer along the A branch are discussed. Two bound detergent molecules of beta-octyl glucoside have been located near BA and BB. The environment of the carotenoid, C, that is present in RCs from Rb. sphaeroides 2.4.1 consists largely of aromatic residues of the M subunit. A role of BB in the triplet energy transfer from D to C and the reason for the preferential ease of removal of BB from the RC is proposed.
Bacteriochlorophylls↗
Structure of the reaction center from Rhodobacter sphaeroides R-26: protein-cofactor (quinones and Fe2+) interactions.
The three-dimensional structure of the reaction center (RC) from Rhodobacter sphaeroides has been determined by x-ray diffraction to a resolution of 2.8 A with an R value of 24%. The interactions of the protein with the primary quinone, QA, secondary quinone, QB, and the nonheme iron are described and compared to those of RCs from Rhodopseudomonas viridis. Structural differences between the QA and QB environments that contribute to the function of the quinones (the electron transfer from QA- to QB and the charge recombination of QA-, QB- with the primary donor) are delineated. The protein residues that may be involved in the protonation of QB are identified. A pathway for the doubly reduced QB to dissociate from the RC is proposed. The interactions between QB and the residues that have been changed in herbicide-resistant mutants are described. The environment of the nonheme iron is compared to the environments of metal ions in other proteins.
Bacterial Proteins↗
Structure of the reaction center from Rhodobacter sphaeroides R-26 and 2.4.1: symmetry relations and sequence comparisons between different species.
Photosynthetic reaction centers from purple bacteria exhibit an approximate twofold symmetry axis, which relates both the cofactors and the L and M subunits. For the reaction center from Rhodobacter sphaeroides, deviations from this twofold symmetry axis have been quantitated by superposing, by a 180 degrees rotation, the cofactors of the B branch onto the A branch and the M subunit onto the L subunit. An alignment of the sequences of the L and M subunits from four purple bacteria, one green bacterium, and the D1 and D2 subunits of a photosystem II-containing green alga is presented. The residues that are conserved in all six species are shown in relation to the structure of Rb. sphaeroides and their possible role in the function of the reaction center is discussed. A method is presented for characterizing the exposure of alpha-helices to the membrane based on the periodicity of conserved residues. This method may prove useful for modeling the three-dimensional structures of membrane proteins.
Amino Acid Sequence↗