Coupled transport

Facilitated transport membranes can be used to separate gases membrane transport is then driven by a difference in the gas partial pressure across the membrane. Metal ions can also be selectively transported across a membrane driven by a flow of hydrogen or hydroxyl ions in the other direction. This process is sometimes called coupled transport. 

In this chapter, we have examined coupled transport systems that rely on ATP hydrolysis, on primary gradients of Na or Ff, and on phosphotransferase systems. Suppose you have just discovered an unusual strain of bacteria that transports rhamnose across its plasma membrane. Suggest experiments that would test whether it was linked to any of these other transport systems. 

JS Patton. Is the intestinal membrane bilayer freely permeable to lipophilic molecules In F Alvarado, CH van Os, eds. Ion Gradient-Coupled Transport. INSERM Symposium No. 26. Amsterdam Elsevier Science, 1986, pp 33-36. 

Boll, M., et al. Expression cloning of a cDNA from rabbit small intestine related to proton-coupled transport of peptides, beta-lactam antibiotics and ACE-inhibitors. Pflugers Arch. 1994, 429, 146-149. 

Tamai I, China K, Sai Y, Kobayashi D, Nezu J, Kawahara E et al. Na(+)-coupled transport of L-carnitine via high-affinity carnitine transporter OCTN2 and its sub-cellular localization in kidney. Biochim Biophys Acta 2001 1512(2) 273-284. 

Van Cappellen, P. Wang Y. 1996. Cycling of iron and manganese in surface sediments a general theory for the coupled transport and reaction of carbon, oxygen, nitrogen, sulfur, iron and manganese. American Journal Sciences, 296, 197-243. 

Glutamate and sodium/lithium-induced conformational changes in the GLT-1 transporter have been detected by the altered accessibility of trypsin-sensitive sites to the protease (59). These experiments in GLT-1 shows that lithium can occupy at least one of the sodium ion binding sites, but lithium by itself cannot support coupled transport (59). Therefore, at least one of the sodium binding sites in GLT-1 discriminates between sodium and lithium. As described earlier, this contrasts with EAAC-1, where lithium is able to support uptake. It should therefore be possible to identify residues that are responsible for the sodium/lithium selectivity difference between EAAC-1 and GLT-1. 

Williams, K. A. (2000) Three-dimensional structure of the ion-coupled transport protein NhaA. Nature 403,112-115. 

With respect to the driving forces and the modes of energy coupling, transport processes can be divided in four major classes ... 

Eukaryotic ABC transport system Phosphotransferase system (PTS) Ion-coupled transport system Signal Transduction Two-component system Bacterial chemotaxis MAPK signaling pathway Second messenger signaling pathway Ligand-Receptor Interaction G-protein-coupled receptors Ion-channel-linked receptors Cytokine receptors Molecular Assembly Ribosome assembly Flagellar assembly Enzyme assembly... 

The thermodynamics of insertion electrodes is discussed in detail in Chapter 7. In the present chapter attention is focused mainly on the general kinetic aspects of electrode reactions and on the techniques by which the transport of species within electrodes may be determined. The electrodes are treated in a general fashion as exhibiting mixed ionic and electronic transport, and attention is concentrated on the description of the coupled transport of these species. In this context it is useful to consider that an electronically conducting lead provides the electrons at the electrodes and compensates the charges of the ions transferred by the electrolyte. 

Tamai, L, Takanaga, H., Maeda, H., Yabuuchi, H., Sai, Y., Suzuki, Y., and Tsuji, A., Intestinal brush-border membrane transport of monocarboxylic acids mediated by proton-coupled transport and anion antiport mechanisms, J. Pharm. Pharmacol, 49, 108, 1997. 

The permeation of cephalosporin antibiotics in an SLM system under reactive extraction condition can be considered a coupled transport phenomenon which can describe metal ion permeation behavior. Various steps are involved in the coupled transport in the SLM system ... 

Step 1 the P ion, after diffusing to the feed-SLM interface, reacts with QCl (Eq. 4) forming a solute-carrier complex, QP CL ions are simultaneously released into the feed solution (coupled transport). 

Step 3 at the SLM-stripping interface, QP releases P ions into the aqueous phase, CL ions replace P ions in the membrane (coupled transport). 

Lovric M, Scholz F (1999) A model for the coupled transport of ions and electrons in redox conductive microcrystals, J Solid State Electrochem 3 172-175. 

The idea of disposed redox reactions inside or across membranes for the purposes of coupling transport to metabolism has been discussed for a long time, especially in the last 15 years. The origin of these ideas goes back many more years, (e.g., Ogston and Davies, about 1950) but was revitalized by P. Mitchell and myself in 1961. A review is given by P. Mitchell, FEBS Lett. 78, 1-20 (1977). 

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