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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/05/30 11:11:07」(JST)

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A symporter is an integral membrane protein that is involved in movement of two or more different molecules or ions across a phospholipid membrane such as the plasma membrane in the same direction, and is, therefore, a type of cotransporter. Typically, the ion(s) will move down the electrochemical gradient, allowing the other molecule(s) to move against the concentration gradient. The movement of the ion(s) across the membrane is facilitated diffusion, and is coupled with the active transport of the molecule(s). Although two or more types of molecule are transported, there may be several molecules transported of each type.

Examples

SGLT1 in the intestinal epithelium transports sodium ions (Na⁺) and glucose across luminal membrane of the epithelial cells so that it can be absorbed into the bloodstream. This is the basis of oral rehydration therapy. If this symporter did not exist, individual sodium channels and glucose uniporters would not be able to transfer glucose against the concentration gradient and into the bloodstream.

Na⁺/K⁺/2Cl^- symporter in the loop of Henle in the renal tubules of the kidney transports 4 molecules of 3 different types; a sodium ion (Na⁺), a potassium ion (K⁺) and two chloride ions (2Cl^-). Loop diuretics such as furosemide (Lasix) act on this protein.

In the roots of plants, the H+/K+ symporters are only one member of a group of several symporters/antiporters that specifically allow only one charged hydrogen ion (more commonly known as a proton) and one charged K+ ion. This group of carriers all contribute to modulate the chemiosmotic potential inside the cell. Initially H+ is pumped into the area outside the root by H+ ATPase. This change in both the pH and electrochemical potential gradient between the inside of the cell and the outside produces a proton motive force, as the protons will want to naturally flow back into the area of low concentration and with a voltage closer to zero from their current situation of being in an area of high concentration of positively charged protons.

The reasons for this are twofold. For one, substances in nature have a tendency to move from areas of high concentration to areas of low concentration, as is evident by dropping a drop of food coloring in a glass of water. It does not aggregate, but begins to move from the highly concentrated areas (the colored areas) to the areas of low concentration (clear areas). Second, large groups of predominantly positively charged or negatively charged particles will naturally repel each other. This is demonstrated by attempting to push the two positive poles or two negative poles of a magnet together. Depending on the strength of the magnet, the repulsion may be so strong that it is impossible to push the magnets together unless aided by machinery. Proton motive force does work on the system by bringing ions back towards the epidermis of the root or surface of a root hair along with the protons. From the surface of the soil/root interface, specific carriers, like H+/K+ symporters allow the specific ions to come into the cell and the out the plasmodesmata/symporters/anitporters of the side of the cell facing away from the soil so that the essential element can make its way up the plant to the area it is needed so that it may supply the plant with important nutrients that are vital to the plant's being able to reach maturity.

The H+/K+ symporter, also called a proton pump, is used to increase acidity of stomach acid. Proton pump inhibitors irreversibly inhibit this enzyme, and so are used as pharmaceuticals whose main action is a pronounced and long-lasting reduction of gastric acid production.

External links

Symporters at the US National Library of Medicine Medical Subject Headings (MeSH)

UpToDate Contents

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1. Chapter 3C：近位尿細管における分泌経路 chapter 3c secretory pathways in proximal tubule
2. ヨード誘発性甲状腺機能異常症 iodine induced thyroid dysfunction
3. 小児における先天性および後天性の甲状腺腫 congenital and acquired goiter in children
4. 甲状腺ホルモンの作用 thyroid hormone action
5. 分化型甲状腺癌の放射性ヨード治療 radioiodine treatment of differentiated thyroid cancer

English Journal

Functional mechanisms of neurotransmitter transporters regulated by lipid-protein interactions of their terminal loops.

Khelashvili G1, Weinstein H2.
Biochimica et biophysica acta.Biochim Biophys Acta.2015 Sep;1848(9):1765-74. doi: 10.1016/j.bbamem.2015.03.025. Epub 2015 Apr 4.
The physiological functions of neurotransmitter:sodium symporters (NSS) in reuptake of neurotransmitters from the synapse into the presynaptic nerve have been shown to be complemented by their involvement, together with non-plasma membrane neurotransmitter transporters, in the reverse transport of s
PMID 25847498

Molecular mechanisms of human thyrocyte dysfunction induced by low concentrations of polychlorinated biphenyl 118 through the Akt/FoxO3a/NIS pathway.

Guo H1, Yang H1, Chen H1, Li W1, Tang J1, Cheng P1, Xie Y1, Liu Y2, Ding G2, Cui D1, Zheng X1, Duan Y1.
Journal of applied toxicology : JAT.J Appl Toxicol.2015 Sep;35(9):992-8. doi: 10.1002/jat.3032. Epub 2015 Feb 2.
Polychlorinated biphenyls (PCBs) are typical persistent organic pollutants that can interfere with multiple organ systems of humans. Previously, we concluded that persistent exposure to low doses of PCB118 could severely damage the thyroidal structure, dramatically decrease the concentration of seru
PMID 25644787

Role of the Transporter-Like Sensor Kinase CbrA in Histidine Uptake and Signal Transduction.

Zhang XX1, Gauntlett JC2, Oldenburg DG2, Cook GM3, Rainey PB4.
Journal of bacteriology.J Bacteriol.2015 Sep 1;197(17):2867-78. doi: 10.1128/JB.00361-15. Epub 2015 Jul 6.
CbrA is an atypical sensor kinase found in Pseudomonas. The autokinase domain is connected to a putative transporter of the sodium/solute symporter family (SSSF). CbrA functions together with its cognate response regulator, CbrB, and plays an important role in nutrient acquisition, including regulat
PMID 26148710

Japanese Journal

Improvement of Ethanol Production from D-Lactic Acid by Constitutive Expression of Lactate Transporter Jen1p in Saccharomyces cerevisiae

WAKAMATSU Makoto,TOMITAKA Masataka,TANI Tatsunori [他]
Bioscience, Biotechnology, and Biochemistry 77(5), 1114-1116, 2013-05
NAID 40019653691

Role of Asp187 and Gln190 in the Na^+/proline symporter (PutP) of Escherichia coli

Amin Anowarul,Ando Tadashi,Saijo Shinya [他],YAMATO Ichiro
The journal of biochemistry 150(4), 395-402, 2011-10-01
NAID 10030588053

Combined Cerenkov luminescence and nuclear imaging of radioiodine in the thyroid gland and thyroid cancer cells expressing sodium iodide symporter : Initial feasibility study

JEONG Shin Young,HWANG Mi-Hye,KIM Jung Eun,KANG Sungmin,PARK Jeong Chan,YOO Jeongsoo,HA Jeoung-Hee,LEE Sang-Woo,AHN Byeong-Cheol,LEE Jaetae
Endocrine journal 58(7), 575-583, 2011-07-01
NAID 10029589363

Related Pictures

★リンクテーブル★

リンク元	「cotransporter」「シンポーター」
拡張検索	「sodium-bicarbonate symporter」「sodium-potassium-chloride symporter inhibitor」「sodium-potassium-chloride symporter」