Electroneutral sodium bicarbonate exchanger 1 is a protein that in humans is encoded by the SLC4A8 gene.
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In molecular biology, the electroneutral cation-Cl (electroneutral potassium chloride cotransporter) family of proteins are a family of solute carrier proteins. This family includes the products of the Human genes: SLC12A1, SLC12A1, SLC12A2, SLC12A3, SLC12A4, SLC12A5, SLC12A6, SLC12A7, SLC12A8 and SLC12A9. The K-Cl co-transporter (KCC) mediates the coupled movement of K+ and Cl− ions across the plasma membrane of many animal cells. This transport is involved in the regulatory volume decrease in response to cell swelling in red blood cells, and has been proposed to play a role in the vectorial movement of Cl− across kidney epithelia.
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Acid secretion by the human stomach results in a median diurnal pH of 1.4. This very large (>106-fold) H+ gradient is generated by the gastric H+/K+ ATPase which is an ATP-driven proton pump. Hydrolysis of one ATP molecule is used to catalyse the electroneutral exchange of two luminal potassium ions for two cytoplasmic protons through the gastric membrane.
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Pendrin is responsible for mediating the electroneutral exchange of chloride (Cl−) for bicarbonate (HCO3−) across a plasma membrane in the chloride cells of freshwater fish. By phylogenetic analysis, pendrin has been found to be a close relative of prestin present on the hair cells or organ of corti in the inner ear. Prestin is primarily an electromechanical transducer but pendrin is an ion transporter.
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Hydrochlorothiazide belongs to thiazide class of diuretics. It reduces blood volume by acting on the kidneys to reduce sodium (Na+) reabsorption in the distal convoluted tubule. The major site of action in the nephron appears on an electroneutral NaCl co-transporter by competing for the chloride site on the transporter. By impairing Na+ transport in the distal convoluted tubule, hydrochlorothiazide induces a natriuresis and concomitant water loss.
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ZCCHC18 is a human protein with 403 amino acids in length and has a predicted molecular weight of 45,160 daltons. Its basal isoelectric point is 7.02 (unphosphorylated state), and isoelectric point decreased with increased number of residues being phosphorylated. The common sequences of ZCCHC18 include KRED and LVIFM. It is generally electroneutral (there are no positive or negative charge clusters or segments) with no high hydrophobic segments.
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Animals have a gastric hydrogen potassium ATPase or H+/K+ ATPase that belongs to the P-type ATPase family and functions as an electroneutral proton pump. This pump is found in the plasma membrane of cells in the gastric mucosa and functions to acidify the stomach. This enzyme is a P2C ATPase, characterized by having a supporting beta-subunit, and is closely related to the Na+/K+ ATPase.
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Prokaryotic and eukaryotic proteins cluster separately but may function with the same polarity by similar mechanisms. These proteins are secondary carriers which utilize the proton motive force (pmf) and function by H+ antiport (for metal efflux). One member, CzcD of Bacillus subtilis (TC# 2.A.4.1.3) , has been shown to exchange the divalent cation (Zn2+ or Cd2+ ) for two monovalent cations (K+ and H+ ) in an electroneutral process energized by the transmembrane pH gradient.
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Human MATE1 (hMATE1) is an electroneutral H+/organic cation (OC) exchanger responsible for the final excretion step of structurally unrelated toxic organic cations in kidney and liver. Glu273, Glu278, Glu300 and Glu389 are conserved in the transmembrane regions. Substitution with alanine or aspartate reduced export of tetraethylammonium (TEA) and cimetidine, and several had altered substrate affinities. Thus, all of these glutamate residues are involved in binding and/or transport of TEA and cimetidine, but their roles are different.
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In addition to the Na+-independent anion exchangers (AE1-3) and the Na+:HCO cotransporters (NBCs) (which may be either electroneutral or electrogenic), a Na+-driven HCO/Cl− exchanger (NCBE) has been sequenced and characterized. It transports Na+ \+ HCO preferentially in the inward direction and H+ \+ Cl− in the outward direction. This NCBE is widespread in mammalian tissues where it plays an important role in cytoplasmic alkalinization. For example, in pancreatic β-cells, it mediates a glucose-dependent rise in pH related to insulin secretion.
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The prestin protein shows several parallel amino acid replacements in bats, whales, and dolphins that have independently evolved ultrasonic hearing and echolocation, and these represent rare cases of convergent evolution at the sequence level. Prestin (mol. wt. 80 kDa) is a member of a distinct family of anion transporters, SLC26. Members of this family are structurally well conserved and can mediate the electroneutral exchange of chloride and carbonate across the plasma membrane of mammalian cells, two anions found to be essential for outer hair cell motility.
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H+/K+ ATPase is a P2-type ATPase, a member of the eukaryotic class of P-type ATPases. Like the Ca2+ and the Na+/K+ ATPases, the H+/K+ ATPase functions as an α, β protomer. Unlike other eukaryotic ATPases, the H+/K+ ATPase is electroneutral, transporting one proton into the stomach lumen per potassium retrieved from the gastric lumen. As an ion pump the H+/K+ ATPase is able to transport ions against a concentration gradient using energy derived from the hydrolysis of ATP.
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The sodium-chloride symporter (also known as Na+-Cl− cotransporter, NCC or NCCT, or as the thiazide-sensitive Na+-Cl− cotransporter or TSC) is a cotransporter in the kidney which has the function of reabsorbing sodium and chloride ions from the tubular fluid into the cells of the distal convoluted tubule of the nephron. It is a member of the SLC12 cotransporter family of electroneutral cation-coupled chloride cotransporters. In humans, it is encoded by the gene SLC12A3 (solute carrier family 12 member 3) located in 16q13. A loss of NCC function causes Gitelman syndrome, an autosomic recessive disease characterized by salt wasting and low blood pressure, hypokalemic metabolic alkalosis, hypomagnesemia and hypocalciuria.
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The sodium-chloride symporter or NCC is a member of the SLC12 cotransporter family of electroneutral cation-coupled chloride cotransporter, along with the potassium-chloride cotransporters (K+-Cl− cotransporters or KCCs), the sodium- potassium-chloride cotransporters (Na+-K+-Cl− cotransporters or NKCCs) and orphan member CIP (cotransporter interacting protein) and CCC9. The sodium- chloride symporter's protein sequence has a high degree of identity between different mammalian species (over 90% between human, rat and mouse). The SLC12A3 gene encodes for a protein of 1,002 to 1,030 amino acid residues. NCC is a transmembrane protein, presumed to have a hydrophobic core of either 10 or 12 transmembrane domains with intracellular amino- and carboxyl-terminus domains.
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The transport process involves one for one electroneutral movement of K+ together with Cl−, and, in all known mammalian cells, the net movement is outward. The neuronal KCC subtype KCC2 is cell- volume insensitive and plays a unique role in maintaining low intracellular Cl−concentration, which is required in neurones for the functioning of Cl− dependent fast synaptic inhibition, mediated by certain neurotransmitters, such as gamma-aminobutyric acid (GABA) and glycine. Three isoforms of the K-Cl co-transporter have been described, termed KCC1 (SLC12A4), KCC2 (SLC12A5), and KCC3 (SLC12A6), containing 1085, 1116 and 1150 amino acids, respectively. They are predicted to have 12 transmembrane (TM) regions in a central hydrophobic domain, together with hydrophilic N- and C-termini that are likely cytoplasmic.
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Current source density analysis (which could more accurately be called current source and sink density analysis) is the practice of placing a microelectrode in proximity to a nerve or a nerve cell to detect current sourcing from, or sinking into, their plasma membranes. When positive charges, for example, flow quickly across a plasma membrane to the inside of a cell (sink) this creates a transient cloud of negativity in the vicinity of the sink. This is because the flow of positive charges into the interior of the cell leaves behind uncompensated negative charges. A nearby micro-electrode with substantial tip resistance (on the order of 1 MΩ) can detect that negativity because a voltage difference will develop across the tip of the electrode (between the negativity outside the electrode, and the electroneutral environment inside the electrode).
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The bond valence model can be reduced to the traditional ionic model if certain conditions are satisfied. These conditions require that atoms be divided into cations and anions in such a way that (a) the electronegativity of every anion is equal to, or greater than, the electronegativity of any of the cations, (b) that the structure is electroneutral when the ions carry charges equal to their valence, and (c) that all the bonds have a cation at one end and an anion at the other. If these conditions are satisfied, as they are in many ionic and covalent compounds, the electrons forming a bond can all be formally assigned to the anion. The anion thus acquires a formal negative charge and the cation a formal positive charge, which is the picture on which the ionic model is based.
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The electroneutral symport of phosphate ion and H+ results in importing one proton, without its charge, per phosphate. Taken together, import of ADP and Pi and export of the resulting ATP results in one proton imported, subtracting from the number available for use by the ATP synthase directly. Taking this into account, it takes 8/3 +1 or 3.67 protons for vertebrate mitochondria to synthesize one ATP in the cytoplasm from ADP and Pi in the cytoplasm. Within aerobic respiration, the P/O ratio continues to be debated; however, current figures place it at 2.5 ATP per 1/2(O2) reduced to water, though some claim the ratio is 3. This figure arises from accepting that 10 H+ are transported out of the matrix per 2 e−, and 4 H+ are required to move inward to synthesize a molecule of ATP.
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