Membrane topology

Transmembrane Signaling. Figure 2 Membrane topology of receptors that are associated with effector proteins. Upon binding to their cognate ligands (cyan), receptor proteins without intramolecularly linked effector domain couple via transducer proteins (yellow) to or directly recruit and activate effector proteins (red). Notch receptors release their transducer domains upon proteolytic cleavage, a, p and y stand for G-protein a-, p- and y-subunits, respectively. 

The principal difference in the overall protein composition of PNS and CNS myelin is that P0 replaces PLP as the major protein, although myelin-forming Schwann cells do express very low levels of PLP. It is interesting to note that PLP and P0 proteins, which are so different in sequence, post-translational modifications and membrane topology, may have similar roles in the formation of structures as closely related as myelin of the CNS and PNS respectively. Expression of P0 in transfected cells results in cell-cell interactions that are due to homophilic binding... 

Bennett, E. R. and Kanner, B. I. (1997) The membrane topology of GAT-1, a (Na+ + decoupled gamma-aminobutyric acid transporter from rat brain. J. Biol. Chem. 272, 1203-1210. 

It is believed that the Gaussian bending modulus k controls the membrane topology. In particular, a negative value of this constant is needed for stable bilayers. A positive value will induce nonlamellar topologies, such as bicontinuous cubic phases. Therefore, it is believed that k is negative for membranes. 

Figure 7.10 Predicted membrane topologies for the ZIP/SLC39 and CDF/Znt/SLC30 families of metal ion transporters. (From Eide, 2006. Copyright 2006, with permission from Elsevier.)...

The idea of finding the best model was extended by Jones et al. (1994). A dynamic programming algorithm was used to select the most plausible model, and the same authors also presented an ambitious method to predict the three-dimensional structure of the a-helical membrane proteins (Taylor etal., 1994). Finally, HMMs were used to model the overall structure of the membrane topology by two groups of researchers (Sonn-hammer et al., 1998 Tusnady and Simon, 1998). 

T. Friedberg, R. Holler, B. Lollmann, M. Arand, F. Oesch, The Catalytic Activity of the Endoplasmic Reticulum-Resident Protein Microsomal Epoxide Hydrolase towards Carcinogens Is Retained on Inversion of Its Membrane Topology , Biochem. J. 1996, 319, 131 - 136. 

Q. Zhu, P. von Dippe, W. Xing, D. Levy, Membrane Topology and Cell Surface Targeting of Microsomal Epoxide Hydrolase. Evidence for Multiple Topological Orientations , J. Biol. Chem. 1999, 274, 27898 - 27904. 

Figure 10.1. The membrane topology proposed for D. vulgaris Hildenborough DcrH based on hydrophathy analysis and sequence homologies to other bacterial chemoreceptors (Deckers and Voordouw 1996). Shaded boxes, putative membrane-spanning (residues 9-30 and 422 31), excitation (residues 653-692), and methylation (residues 757-764) regions. The C-terminal box (residues 824-959) indicates the Hr-like region. Reprinted with permission from Xiong et al. (2000), copyright 2000 American Chemical Society.

Figure 5.4 Membrane topology for the Shaker potassium ion channel with important residues circled. (Adapted with permission from Figure lA of reference 29. Copyright 2003, with permission from Elsevier.)...

Fig. 2. a2-Adrenergic receptor subtypes. The putative membrane topology of the three mouse a2-receptor subtypes is schematically depicted. Open circles represent amino acids which are identical between all subt es, gray circles represent amino acids which are conserved among two subtypes, dark circles are non-identical amino acids. Tissue distribution of tt2-receptor subtypes is based on mRNA and protein expression references are given in the text... 

Yardeny Y., H. Rodriguez, S.K.-F. Wong, D.R. Brandt, D.C. May, J. Bumier, R.N. Harkins, E.Y. Chen, J. Ramachandran, A. Ullrich, and E.M. Ross (1986). The avian beta-adrenergic receptor Primary structure and membrane topology. Proceedings of the National Academy of Science U.S.A. 83 6795-6799. 

Forst, S. Comeau, D. Norioka, S. Inouye, M. Localization and membrane topology of EnvZ, a protein involved in osmoregulation of OmpF and OmpC in Escherichia coli. J. Biol. Chem., 262, 16433-16438 (1987)... 

B) Cleavage of a polypeptide loop formed as in (A) by a leader peptidase to give a polypeptide chain anchored by a positively charged cluster near its C terminus. (C) Membrane topology of the E. coli leader peptidase. The active site is in the periplasmic domain. See Tschantz et al.5S0... 

Ma, J., Hayek, S. M., and Bhat, M. B. (2004). Membrane Topology and Membrane Retention of the Ryanodine Receptor Calcium Release Channel. Cell Biochem Biophys 40(2) 207-24. 

Fig. 5 The snake PLA2 neurotoxin is depicted here as a snake, which binds to an active zone, i.e., a synaptic vesicle (SV) release site, and hydrolyses the phospholipids of the external layer of the presynaptic membrane (green) with formation of the inverted-cone shaped lysophospholipid (yellow) and the cone-shaped fatty acid (dark blue). Fatty acids rapidly equilibrate by trans-bilayer movement among the two layers of the presynaptic membrane. In such a way lysophospholipids, which induce a positive curvature of the membrane, are present in trans and fatty acid, which induce a negative curvature, are present also in cis, with respect to the fusion site. This membrane conformation facilitates the transition from a hemifusion intermediate to a pore. Thus, the action of the toxin promotes exocytosis of neurotransmitter (NT) (from the left to the right panel) and, for the same membrane topological reason, it inhibits the opposite process, i.e., the fission of the synaptic vesicle.

Olender E. H. and Simoni R. D. (1992) The intracellular targeting and membrane topology of 3-hydroxy-3-methylglutaryl coenzyme A reductase. J. Biol. Chem. 267, 4223-4235. 

Nomenclature, Basic Structure, and Membrane Topology of MDR Proteins 204... 

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