Isolation, of receptors

Addition of 81-SH to 80-SS-81 led to formation of the homodisulfide compounds and an equilibrium, with an exchange constant of 1.8, was established. The presence of the templating (D)Pro(L)Val(D)Val tri-peptide in this mixture, shifted the equilibrium dramatically and the formation of the homodisulfide 80-SS-80 was amplified with a Keq=32. Since the templating tri-peptide was supported on polymer beads, the isolation of receptor 80-SS-80 (in 97% purity) was achieved easily by extraction of the beads. The formation of multiple hydrogen bonds between the template and the components of the DCL, led to the isolation of the best possible receptor available from the building blocks present in the equilibrated mixture. 

Scheme 3.7 Amplification and isolation of receptors from a DCL using a solid supported template.

Highly specific protein-protein interactions play a large role in many natural biological processes. For instance, the transport and transmission of information proceed via highly specific receptors that can frequently interact with only one molecular species (e.g., hormone or transmitter). In spite of this, the affinity chromatographic isolation of receptors and other highly specific proteins is rather an exception. However, antibodies occupy a special position as monospecific macromolecular ligands. 

The tagging of membrane receptors with traceable agonists or inhibitors is not only employed in procedures for the isolation of receptor complexes from the membrane but can be used for the... 

The isolation of receptor-bound oligonucleotides is much faster and 4 No radioactivity is needed... 

Binding Reaction and Isolation of Receptor-Bound Oligonucleotides... 

There should be specific, saturable binding to the receptor, accompanied by pharmacological characteristics appropriate to the functional effects, demonstrable using a radioactive, eg, tritium or iodine-125, ligand to label the receptor. Radioligand binding assays (1,6) have become a significant means by which to identify and characterize receptors and enzymes (see Immunoassays Radioactive tracers). Isolation of the receptor or expression of the receptor in another cell, eg, an oocyte can be used to confirm the existence of a discrete entity. 

Other specific discovery assays have been used such as differential inhibition of a vancomycin resistant S. aureus strain and its susceptible parent, and an assay based on antagonism of the antibacterial activity by N,A/-diacetyl-L-Lys-D-Ala-D-Ala [24570-39-6] a tripeptide analogue of the dalbaheptides receptor. AppHcation of this latter test to 1936 cultures (90) led to the isolation of 42 dalbaheptides, six of which, including kibdelin (Table 3), parvodicin (Table 3), and actinoidin A2 (68) were novel. A colorimetric assay based on competition between horseradish peroxidase bound teicoplanin and the... 

Previously, pharmacologists were constrained to the prewired sensitivity of isolated tissues for agonist study. As discussed in Chapter 2, different tissues possess different densities of receptor, different receptor co-proteins in the membranes, and different efficiencies of stimulus-response mechanisms. Judicious choice of tissue type could yield uniquely useful pharmacologic systems (i.e., sensitive screening tissues). However, before the availability of recombinant systems these choices were limited. With the ability to express different densities of human target proteins such as receptors has come a transformation in drug discovery. Recombinant cellular systems can now... 

The binding and activation steps of receptor action have been dissected computationally, although not yet in a global fashion. The conformational dynamics of the activation of the A3AR have been approximated with respect to isolated portions of the receptor. 

The molecular weight of isolated IP3 receptor protein is about 225 kDa but the actual receptor is apparently a tetramer. The IP3 receptor is slightly smaller in size than the ryanodine receptor which is also a tetramer. Also, like the ryanodine receptor, Ca ion binding has a synergistic effect on the IP3 receptor. As one might expect, these two receptors have a large sequence homology. There is not much... 

Deng H, Liu R, Ellmeier W, Choe S, Unutmaz D, Burkhart M, Di Marzio P, Marmon S, Sutton RE, Hill CM, Davis CB, Peiper SC, Schall TJ, Littman DR, Landau NR (1996) Identification of a major co-receptor for primary isolates of HIV-1. Nature 381 661-666 Derdeyn CA, Decker JM, Sfakianos JN, Wu X, O Brien WA, Ratner L, Kappes JC, Shaw GM, Hunter E (2000) Sensitivity of human immunodeficiency virus type 1 to the fusion inhibitor T-20 is modulated by coreceptor specificity defined by the V3 loop of gpl20. J Virol 74 8358-8367... 

Research in this area advanced in the 1970 s as several groups reported the isolation of potent toxins from P. brevis cell cultures (2-7). To date, the structures of at least eight active neurotoxins have been elucidated (PbTx-1 through PbTx-8) (8). Early studies of toxic fractions indicated diverse pathophysiological effects in vivo as well as in a number of nerve and muscle tissue preparations (reviewed in 9-11). The site of action of two major brevetoxins, PbTx-2 and PbTx-3, has been shown to be the voltage-sensitive sodium channel (8,12). These compounds bind to a specific receptor site on the channel complex where they cause persistent activation, increased Na flux, and subsequent depolarization of excitable cells at resting... 

The theories that attempt to describe the initial event in sweet-taste stimulation will be discussed, as will some of the practical attempts to isolate sweet-receptor molecules. Relevant, behavioral data will be examined, particularly where the effects of molecular structure on behavior responses are being evaluated. 

Saito H., Mimmack M., Keveme E.B., Kishimoto J. and Emson P. (1998). Isolation of mouse vomeronasal receptor genes and their co-localization with specific G-protein messenger RNAs. Molec Brain Res 60, 215-227. 

Asch A. S., Barnwell J Silverstein R. L Nachman R. L. Isolation of the thromboplastin membrane receptor. J Clin Invest 1987 79,1054-61. 

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