Membranes convergence

Figure 43-13. Several signal transduction pathways converge on CBP/p300. Ligands that associate with membrane or nuclear receptors eventually converge on CBP/p300. Several different signal transduction pathways are employed. EGF, epidermal growth factor GH, growth hormone PrI, prolactin TNF, tumor necrosis factor other abbreviations are expanded in the text.

Chylomicrons leave the absorptive cell by way of exocytosis. Because they are unable to cross the basement membrane of the blood capillaries, the chylomicrons enter the lacteals, which are part of the lymphatic system. The vessels of the lymphatic system converge to form the thoracic duct that drains into the venous system near the heart. Therefore, unlike products of carbohydrate and protein digestion that are transported directly to the liver by way of the hepatic portal vein, absorbed lipids are diluted in the blood... 

Nanosized supramolecular materials have received increasing attention during the last two decades. Their properties have been surveyed for their ability to form aggregates in the solution phase, which form channel-like arrays in the solid state, and which ultimately form single channels in planar bilayer membranes. These systems therefore illustrate, in general, the convergence of supramolecular selforganization and supramolecular function. 

Nelson At high K+ there is a convergence, but at lower K+ the K+ equilibrium potential and the membrane potential are different. A K+ channel opener can still work at low (e.g. 20 mM) K+. 

Grossfield, A., Feller, S.E., Pitman, M.C. Convergence of molecular dynamics simulations of membrane proteins. Proteins Struct. Funct. Bioinformatics 2007, 67, 31 10. 

Cyclodextrin-substituted molecular channel approaches have now been extended to include acyl substituents through a covalent bond formation. Stearoyl and methyl cholate-substituted cyclodextrins 10 and 11, respectively, have been synthesized. It may be worthwhile commenting on the molecular design of methyl cholate-substituted a-cyclodextrin. All of the ether groupings are convergent at the inner side of the steroidal backbone of a bent structure to make the molecule amphiphilic. Once the cyclodextrin derivative is incorporated into the membrane phase, it may easily be expected that the ether parts are assembled inside the channel in the sea of hydrophobic lipid molecules and the hydrophobic steroidal skeletons cover its outside to stabilize the inner hydrophilic pore (Figure 13). 

All these pathways converge to modulate the activity of the enzyme, H+/K+ ATPase, the proton pump of the parietai ceii. This is a membrane-spanning protein, an ATP-dependent ion pump, exchanging K+ and H+ ions. 

Figure 8.4 shows the data [2] of the UF of serum solutions with a hollow fiber-type ultrafilter, with hollow fibers 16 cm in length and 200 pm in i.d., at four shear rates on the inner surface of the hollow-fiber membrane. Slopes of the straight lines, which converge at a point C = Cq on the abscissa, give values at the shear rates given in the figure. 

R. Madsen, U. E. Udodong, C. Roberts, D. R. Mootoo, P. Konradsson, and B. Fraser-Reid, Studies related to synthesis of glycophosphatidyl inositol membrane bound protein anchors Part VI. Convergent assembly of sub-units, J. Am. Chem. Soc. 777 1554 (1995). 

Phosphorylated IRS-1 activates a second signaling pathway by interacting with an 85-kDa SH2-containing protein that is a subunit of phophatidylinositol 3-kinase.384 386 This activates the 110-kDa catalytic subunit of the 3-kinase, which catalyzes formation of phosphatidylinositol 3-phosphate as well as Ptdlns (3,4)P2 and Ptdlns (3,4,5)P3.387/387a These compounds, which remain within membranes, activate other branches of the signaling cascade, some of which may converge with those of the MAP kinase cascade. However, there appears to be specific activation of a ribosomal Ser/Thr kinase that, among other activities, phosphorylates ribosomal protein S6, a component of the small ribosomal subunit.388 It also phosphorylates some isoforms of protein kinase C and other enzymes. Ptdlns 3-kinase may also activate 6-phosphofructo-2-kinase (Fig. 11-2, step ti).384/388... 

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