Membrane receptors isolation

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

Most receptors (a notable exception being the steroid receptors that influence DNA transcription) are located on the cell surface, and purified cell membranes are thus an obvious choice of preparation. When a tissue is homogenized, however, any membrane fraction isolated may well contain membranes from intracellular organelles in addition to cell membranes from all the cell types present in the tissue. Thus, brain membranes will contain membranes not only from neurons but... 

The Fur protein regulates iron uptake systems in many Gram-negative bacteria. The striking phenotype of the first fur mutants isolated was the overexpression of the outer membrane receptors for siderophore iron transport. In addition, excretion of siderophores under iron-rich growth conditions was observed in these mutants, indicating that the biosynthesis of siderophores is also regulated by Fur. 

Every cell possesses a plasma (or cell) membrane which isolates its contents from its surroundings. This membrane consists of a double layer of phospholipid molecules with proteins attached or dispersed within. The uneven distribution of proteins and their ability to move in the plane of the membrane led to the description of this structure as a fluid mosaic (Figure 1.2) (Chapter 5). Some of these proteins facilitate the transport of molecules and ions through the membrane, while others are receptors for extracellular molecules which provide information about conditions in adjacent cells, blood and elsewhere in the body. Physical or chemical damage to these membranes can render them leaky so that, for example, Na and Ca ions, the concentrations of which are much higher in the extracellular fluid, can enter the cell causing damage. On the outer surface of... 

In patients clearance of intravenous heme is rapid until hemopexin levels are depleted (148), and lack of interaction with hemopexin may explain the higher clinical efficacy of heme-arginate compared with hemin itself (149, 150). In intact animals, i.v. heme causes rapid association of hemopexin but not albumin with the liver (47, 63, 68), and heme uptake from heme-albumin complexes into isolated rat hepato-cytes occurs via diffusion of heme released from its loose complex with BSA (137). Moreover, unlike uptake from heme-hemopexin, free heme uptake by cells occurred even at 4°C, as expected for nonspecific membrane association and in total disagreement with a membrane-receptor-mediated or active transport uptake process. 

Hantke K, Nicholson G. Rabsch W, Winkelmann G (2003) Salmochelins, Siderophores of Salmonella enterica and Uropathogenic Escherichia coli Strains, are Recognized by the Outer Membrane Receptor Iron. Proc Natl Acad Sci USA 100 3677 Harada K, Tomita K, Fuji K, Masuda K, Mikami Y, Yazawa K, Komaki H (2004) Isolation and Structural Characterization of Siderophores, Madurastatins, Produced by a Pathogenic Actinomadura madurae. J Antibiot 57 125... 

Dolabella auricularia). Another prominent family of peptides has also been isolated from mollusks these highly compact and stable linear peptides, known as conotoxins, exhibit specific actions on the ion channels and membrane receptors of excitable cells. 

The first step in the biochemical analysis of the receptor, isolation from the cell membrane, was difficult the membrane-associated protein is present in only small amounts and is insoluble in aqueous solution. Sensitivity and selectivity would be improved by radiolabeling under conditions that maintain cell viability so that only proteins associated with the surface and not those within the cell become labeled. A procedure that met these conditions was iodination catalyzed by lactoperoxidase in the presence of hydrogen peroxide (Marchalonis, 1969 Phillips and Morrison, 1970 Marchalonis et al., 1971). It was also necessary to find conditions for solubilizing membrane proteins that would not interfere with subsequent specific immunoprecipitation. 

Intracellular cyclic adenosine monophosphate (cAMP)-stimulated add secretion in the isolated guinea-pig gastric mucosa was not inhibited by administration of an H2-receptor antagonist, as expected, although H 83/69 (timoprazole) induced a dose-dependent inhibition. This was the first experimental evidence for a site of inhibitory action beyond the panel of stimulatory cell membrane receptors. Interestingly, it was found that the initial lead compound (CMN 131), had no inhibitory effect on dibutyryl-cAMP-stimulated acid secretion, nor was it an H2-receptor antagonist [9],... 

Asch AS, Barnwell J, Silverstein RL, Nachman RL Isolation of the thrombospondin membrane receptor. J Clin Invest 79 1054-1061,1987... 

Rat brain cortex membrane was isolated, and the membrane homogenate was used as a preparation containing somatostatin receptors. Four rats were sacrificed by cervical dislocation. The cerebral cortex tissue was washed three times with buffer (HEPES 20niM, pH7.3, containing lOmM MgCl2) and homogenized in ice-cold buffer, using a cortex to buffer ratio of 1 10, at... 

Somatostatin membrane receptor is isolated from rat brain cortices by one of the two methods described below. 

The main active principle of Cannabis, A -tetrahydrocan-nabinol, has been isolated and characterized by Raphael Mechonlam (Jerusalem, Israel) (Figure 1.44) in 1964. The term endocannabinoid coined after the discovery of membrane receptors for this psychoactive principle, indicates... 

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