Membrane topography

Several human receptors for the neurohypophyseal hormones have been cloned and the sequences elucidated. The human V2 receptor for antidiuretic hormone presumably contains 371 amino acids and seven transmembrane segments and activates cycHc AMP (76). The oxytocin receptor is a classic G-protein-coupled type of receptor with a proposed membrane topography also involving seven transmembrane components (84). A schematic representation of the oxytocin receptor stmcture within the membrane is shown in Eigure 4 (85). 

Figure 11.2 The Ca2+ influx channels of the plasma membrane, (a) A voltage-gated channel—the membrane topography of the al-subunit, which forms the channel proper, (b) Membrane topography of TRP channels, homologous to the SOC channels, (c) Membrane topography of the ligand-gated glutamate NMDA receptor. (From Carafoli, 2005. Reproduced with permission from Blackwell...

Pitelka, D.R., B.N. Taggart, and S.T. Hamamotto. 1983. Effects of extracellular calcium depletion on membrane topography and occluding junctions of mammary epithelial cells in culture. J Cell Biol 96 613. 

Fig. 2 Membrane topography of the a-LTX pore. Cross-section of the a-LTX tetramer embedded in a membrane (as observed in liposomes) (Orlova et al. 2000) is shown alongside the cut-open voltage-dependent K+ channel (Kvl.2) (Long et al. 2005) and Ca2+ release channel (ryanodine receptor) (Serysheva et al. 2005). Fully hydrated cations and molecules known to permeate through the respective channels are shown next to each reconstruction (FITC, fluoresceine isothiocyanate NE, norepinephrine). The narrowest part of the a-LTX channel is 10 A. Molecular images were produced using the UCSF Chimera package (Pettersen et al. 2004).

Figure 1 Predicted sequence and membrane topography of the murine delta opioid receptor. The mouse sequence was obtained from Genbank (accession No. L07271). Negatively charged amino acids within TMD 2 and 3 are circled and extracellular N-linked glycosylation sites are indicated ( ). Arrows indicate intron/exon boundaries in the mouse genome. (From Ref. 40.)...

Wang, X., Karbarz, M.J., McGrath, S.C., Cotter, R.J., Raetz, C.R.H. MsbA transporter-dependent lipid A 1-dephosphorylation on the periplasmic surface of the inner membrane topography of Francisella novicida LpxE expressed in Escherichia coli. J Biol Chem 279 (2004) 49470-49478. 

Song HY, Cramer WA (1991) Membrane topography of ColEI gene products the immunity protein. J Bacteriol 173 2935 - 2943... 

The structure and morphology of the membrane also influence its permeability. XRD has been widely applied for the characterization of crystalline structure, especially for confirmation of alloy formation in multicomponent materials and identification of bulk corrosion products. SEM and atomic force microscopy are routinely applied to the characterization of membrane topography and are helpful for identification of failure mechanisms. More advanced methods, including... 

Malenbaum, S.E., Collier, R.J., London, E. Membrane topography of the T domain of diphtheria toxin probed with single tryptophan mutants. Biochemistry 37, 17915-17922 (1998)... 

Heraux F, Sigalat C, Morau A, de Kouchkovsky Y (1983) The efficiency of energized protons for ATP synthesis depends on the membrane topography in thylakoids. FEBS Lett. 155, 248-252. 

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