Pseudoreceptor Model Research Articles

A three-dimensional receptor model for isovanillic sweet derivatives

Using pseudoreceptor modelling, we have derived a three-dimensional binding-site model for the structurally uncharacterised sweet-taste receptor. The receptor model was derived based on 17 sweet compounds of the isovanillyl class (4-methoxy-3-hydroxybenzyl) as the training set and consists of nine key amino-acid residues embedded in a hydrophobic receptor cavity. The underlying technology (software PrGen) allows for a dynamical treatment of the ligand–receptor complex (ligand equilibration and Monte-Carlo scanning of receptor space) as well as for receptor-mediated ligand alignment. Free energies of ligand binding are estimated based on ligand–receptor interactions, ligand desolvation energy, change of ligand internal energy and change of ligand entropy upon receptor binding.

Structure-activity relationships of cannabinoids: a joint CoMFA and pseudoreceptor modelling study.

A cannabinoid pseudoreceptor model for the CB1-receptor has been constructed for 31 cannabinoids using the molecular modelling software YAK. Additionally, two CoMFA studies were performed on these ligands, the first of which was conducted prior to the building of the pseudoreceptor. Its pharmacophore is identical with the initial superposition of ligands used for pseudoreceptor construction. In contrast, the ligand alignment for the second CoMFA study was taken directly from the final cannabinoid pseudoreceptor model. This altered alignment gives markedly improved cross-validated r2 values as compared to those obtained from the original alignment with r2 cross values of 0.79 and 0.63, respectively, for five components. However, the pharmacophore alignment has the better predictive ability. Both the CoMFA and pseudoreceptor methods predict the free energy of binding of test ligands well.

A pseudoreceptor modelling study of the varicella-zoster virus and human thymidine kinase binding sites.

A representative range of pyrimidine nucleoside analogues that are known to inhibit herpes simplex virus (HSV) replication have been used to construct receptor binding site models for the varicella-zoster virus (VZV) thymidine kinase (TK) and human TK1. Given a set of interacting ligands, superimposed in such a manner as to define a pharmacophore, the pseudoreceptor modelling technique Yak provides a means of building binding site models of macromolecules for which no three-dimensional experimental structures are available. Once the models have been evaluated by their ability to reproduce experimental binding data [Vedani et al., J. Am. Chem. Soc., 117 (1995) 4987], they can be used for predictive purposes. Calculated and experimental values of relative binding affinity are compared. Our models suggest that the substitution of one residue may be sufficient to determine ligand subtype affinity.

Pseudoreceptor Modeling: The Construction of Three-Dimensional Receptor Surrogates

Pseudoreceptor Modeling: The Construction of Three-Dimensional Receptor Surrogates

Pharmacophore refinement of gpIIb/IIIa antagonists based on comparative studies of antiadhesive cyclic and acyclic RGD peptides

Structurally guided design approaches to low-molecular-weight platelet aggregation antagonists addressing the platelet-associated heterodimeric cell surface receptor gpIIb/IIIa rely on comparative studies of an ensemble of conformationally and biologically characterized compounds, since no high-resolution structure of the receptor system is available. We report a classical indirect and comparative pharmacophore refinement approach based on a series of small cyclic Arg-Gly-Asp (RGD) peptides as gpIIb/IIIa-fibrinogen interaction antagonists. These peptides have previously been investigated as potent and selective tumor cell adhesion inhibitors. The definition of geometrical descriptors classifying the RGD peptide conformations and their subsequent analysis over selected RGD- and RXD-containing protein structures allows for a correlation of distinct structural features for platelet aggregation inhibition. An almost parallel alignment of the Arg and Asp side chains was identified by a vector analysis as being present in all active cyclic hexa- and pentapeptides. This orientation is induced mainly by the constraint of backbone cyclization and is not of any covalent tripeptide-inherent origin, which was rationalized by a 500 ps high-energy MD simulation of a sequentially related linear model peptide. The incorporation of the recognition tripeptide Arg-Gly-Asp into the cyclic peptide templates acted as a filter mechanism, restricting the otherwise free torsional relation of both side chains to a parallel orientation. Based on the derived results, several detailed features of the receptor binding site could be deduced in terms of receptor complementarity. These findings should govern the design of next-generation compounds with enhanced activities. Furthermore, the complementary stereochemical characteristics of the substrate can be used as boundary conditions for pseudoreceptor modelling studies that are capable of reconstructing a hypothetical binding pocket, qualitatively resembling the steric and electronic demands of gpIIb/IIIa. It is interesting to note that these features provide clear differentiation to requirements for inhibition of alpha v beta 3 substrate binding. This can account for the extremely high selectivity and activity of some of our constrained peptides for either the alpha IIb beta 3 or the alpha v beta 3 receptor.

Pseudoreceptor modeling and the “YAK” concept

Pseudoreceptor modeling and the “YAK” concept

Pseudo-Receptor Modeling: A new Concept for the Three-Dimensional Construction of Receptor Binding Sites

Molecular design of small molecules intended to target a macromolecule generally utilizes one of two computational approaches: "receptor fitting" or "receptor mapping". A comprehensive strategy for the design of potent, selective and novel ligands for cell-bound receptors combines the two by means of "pseudoreceptor modeling". Definition of a refined pharmacophore model is the first step. A subsequent step involves the construction of a pseudoreceptor--an explicit molecular binding pocket--for the bioactive conformation of a series of ligands with high affinity for a particular receptor subtype. The receptor-mapping program "Yak" allows the construction of a peptidic pseudoreceptor around any single small molecule or molecular ensemble of interest. The fidelity of the approach is exemplified by application to the active site of the enzymes human carbonic anhydrase I and thermolysin, followed by comparison with their known X-Ray crystal structures.