Membrane receptors characterization

There are several major classes of Ca channels (1) receptor-operated Ca channels in plasma membranes (2) ligand-gated Ca " channels in intracellular membranes and (3) voltage-dependent Ca channels that are usually found in plasma membranes or the invaginations of the plasma membrane that are known as transverse tubule membranes. Receptor-dependent or receptor-operated Ca channels (ROCCs) are primarily opened in response to activation of their associated receptors and, by definition, exhibit a certain amount of selectivity for Ca " over other cations. Several potentially different types of ROCCs have been characterized including ATP-sensitive channels in smooth muscle [1], mitogen and IP3-sensitive... 

The first of the haem uptake systems to be characterized at molecular level was that of Yersinia enterolitica, which closely resembles a typical siderophore uptake system (Stojiljkovic and Hantke, 1992, 1994), including a TonB-dependent outer membrane receptor for haem, a periplasmic binding protein, and a cytoplasmic membrane transport system. There also seems to be a protein that degrades haem and liberates haem iron within the cell. TonB-dependent outer membrane receptor proteins for haem have been cloned and sequenced from Shigella dysenteriae and E. coli (Mills and Payne, 1995 Torres and Payne, 1997), while in Vibrio cholera two genes are required for haem utilization, one an outer membrane receptor a second which may have a TonB-like function (Henderson and Payne, 1994). 

Extracellular ligands (hormones, neurotrophins, carrier protein, adhesion molecules, small molecules, etc.) will bind to specific transmembrane receptors. This binding of specific ligand induces the concentration of the receptor in coated pits and internalization via clathrin-coated vesicles. One of the best studied and characterized examples of RME is the internalization of cholesterol by mammalian cells [69]. In the nervous system, there are a plethora of different membrane receptors that bind extracellular molecules, including neurotrophins, hormones and other cell modulators, being the best studied examples. This type of clathrin-mediated endocytosis is an amazingly efficient process, capable of concentrating... 

Adkins, C. E., Pillai, G. V., Kerby, J., et al. (2001) alpha4beta3delta GABA(A) receptors characterized by fluorescence resonance energy transfer-derived measurements of membrane potential. J. Biol. Chem. 276, 38934-38939. 

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... 

Macrophage presence and reactivity in tissue sites are elicited though different combinations of effector molecules (e.g., cytokines, chemokines) acting on specific receptors thus, the expression and presence of given membrane receptors on macrophage cell surfaces correlate to specific (acquired) functions and activation profiles.18 Furthermore, macrophage maturity and/or differentiation state is/are often characterized based on the presence or absence of specific surface receptors (e.g., F4/80 +, Mac-1 + Figure 2.1).61 Receptor profiles vary between cells of different maturity, primary and secondary derivation, and between cell lines.62... 

One approach to this problem would be to isolate the intact lectin-receptor molecules from the cell membranes and characterize them. Work in this direction has been initiated in our laboratory, and a method for the isolation of the peanut agglutinin receptor from membranes of neuraminidase-treated human erythrocytes on a column of peanut agglutinin-polyacryl-hydrazido-Sepharose has been developed (21). The amino acid composition, D-glucosamine ancHg-galac-tosamine content, and the electrophoretic mobility on polyacrylamide gel electrophoresis in sodium... 

Characterization of membrane receptors some general considerations... 

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