Solute carrier protein

Other solute transporters (solute carrier protein [SLC]) are also expressed in the alveolus. The mRNA transcripts of glucose transporters, GLUT1, GLUT4, GLUT5 and SGLT1, have been detected in freshly isolated rat ATII cells by... 

Fatty acid transport protein paralogues 1-6 FATP 1-6 Gene symbols SLC27A1-6 Solute carrier family 27A Very long-chain acyl-CoA synthetase VLCS... 

Add 500 pi of the peptide solution to 200 pi of carrier protein. For greater reaction volumes, keep the molar ratio of peptide-to-carrier addition the same and proportionally scale up the amount of EDC added in the next step. If the peptide is initially dissolved in DMSO, much less peptide volume compared to protein volume should be used to maintain solubility (see discussion in step 2). 

After a carrier protein has been activated with sulfo-SMCC, it is often useful to measure the degree of maleimide incorporation prior to coupling an expensive hapten. Ellman s reagent may be used in an indirect method to assess the level of maleimide activity of sulfo-SMCC-activated proteins and other carriers. First, a sulfhydryl-containing compound such as 2-mercaptoethanol or cysteine is reacted in excess with the activated protein. The amount of unreacted sulfhydryls remaining in solution is then determined using the Ellman s reaction (Chapter 1, Section 4.1). Comparison of the response of the sample to a blank reaction using... 

Dissolve sulfo-SMCC (Thermo Fisher) at a concentration of lOmg/ml in the activation buffer. Immediately transfer the appropriate amount of this crosslinker solution to the vial containing the dissolved carrier protein. 

Add the following quantities of sulfo-SMCC solution to each ml of carrier protein solution ... 

Mix 0.5 ml of the peptide solution with 0.5 ml of the carrier protein solution. Chill on ice. Add 0.4 ml of the fois-diazotized tolidine solution. There should be a color change from orange to red almost immediately. Continue the reaction for 2 hours on ice in the dark. 

Figure 1. Solute transfer across an idealised eukaryote epithelium. The solute must move from the bulk solution (e.g. the external environment, or a body fluid) into an unstirred layer comprising water/mucus secretions, prior to binding to membrane-spanning carrier proteins (and the glycocalyx) which enable solute import. Solutes may then move across the cell by diffusion, or via specific cytosolic carriers, prior to export from the cell. Thus the overall process involves 1. Adsorption 2. Import 3. Solute transfer 4. Export. Some electrolytes may move between the cells (paracellular) by diffusion. The driving force for transport is often an energy-requiring pump (primary transport) located on the basolateral or serosal membrane (blood side), such as an ATPase. Outward electrochemical gradients for other solutes (X+) may drive import of the required solute (M+, metal ion) at the mucosal membrane by an antiporter (AP). Alternatively, the movement of X+ down its electrochemical gradient could enable M+ transport in the same direction across the membrane on a symporter (SP). A, diffusive anion such as chloride. Kl-6 refers to the equilibrium constants for each step in the metal transfer process, Kn indicates that there may be more than one intracellular compartment involved in storage. See the text for details...

These methods of solute transfer usually rely on a relatively low intracellular concentration of the solute of interest, so that it will readily diffuse into the cell down the electrochemical gradient (as in the case of ion channels). Alternatively, the solute may be moved into the cell using chemical energy derived from another solute moved in the same direction (co-transport) or opposite direction (countertransport) on the carrier protein (symporters and antiporters respectively). The transfer of the second solute is in turn dependent on an inward electrochemical gradient. Ultimately, these gradients are established by primary, energy-requiring solute pumps (e.g. ATPases), which, on most epithelia, are located on the basolateral/serosal membrane (see Section 5.2 for discussion of ATPases). 

Primary transport the active transport of a solute against the electrochemical gradient by carrier proteins which derive energy for transport directly from the hydrolysis of ATP. 

Figure 15.1 Schematic illustration of the extended phase concept during drug elimination in the kidney and liver. Phase 0 = uptake of drugs from the blood into the hepatocytes or proximal tubule epithelial cells. This uptake is mediated by transport proteins belonging to the SLC (solute carrier) transporter superfamily. Phase I and...

Hediger, M.A., Romero, M.F., Peng, J.B., Rolfs, A., Takanaga, H. and Bruford, E.A. (2004) The ABCs of solute carriers physiological, pathological and therapeutic implications of human membrane transport proteins. Pflugers Archiv, 447, 465-468. 

Blood is the transport medium of the body. Plasma, which accounts for approximately 60% of the total volume, carries a wide range of small and medium-sized metabolites some are simply dissolved in solution (93% of the plasma is water), others are carried by specific carrier proteins. The chemical composition of the plasma is complex and reflects the chemical composition inside cells, which is why blood tests are so commonly used in diagnosis to see the biochemical events occurring in tissues. The formed cellular elements of the blood perform several functions defence against blood loss from bleeding (platelets, also called thrombocytes), defence against infection and immune surveillance (white cells, leucocytes), and gas transport and pH buffering (red cells, erythrocytes). 

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