Halorhodopsin is a , specific for chloride ions, found in archaea, known as halobacteria. It is a seven-transmembrane retinylidene protein from microbial rhodopsin family. It is similar in tertiary structure (but not primary sequence structure) to vertebrate rhodopsins, the pigments that sense light in the retina. Halorhodopsin also shares sequence similarity to channelrhodopsin, another light-driven ion channel. Halorhodopsin contains the essential light-isomerizable vitamin A derivative all-trans-retinal. Due to the intense attention on solving the structure and function of this molecule, halorhodopsin is one of the few membrane proteins whose crystal structure is known.
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| - Halorhodopsin (en)
- Halorhodopsine (fr)
- Halorodopsyna (pl)
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| - Halorhodopsin is a , specific for chloride ions, found in archaea, known as halobacteria. It is a seven-transmembrane retinylidene protein from microbial rhodopsin family. It is similar in tertiary structure (but not primary sequence structure) to vertebrate rhodopsins, the pigments that sense light in the retina. Halorhodopsin also shares sequence similarity to channelrhodopsin, another light-driven ion channel. Halorhodopsin contains the essential light-isomerizable vitamin A derivative all-trans-retinal. Due to the intense attention on solving the structure and function of this molecule, halorhodopsin is one of the few membrane proteins whose crystal structure is known. (en)
- L'halorhodopsine est une protéine transmembranaire formant un canal ionique spécifique aux anions chlorure Cl– chez une classe d'archées particulière appelée Halobacteria. Sa structure est semblable à celle de la bactériorhodopsine, et elle utilise également le rétinal comme cofacteur photosensible. Le pic d'absorption du complexe rétinal-halorhodopsine se situe autour de 570 nm. Ce canal pompe les ions Cl– vers l'intérieur de la cellule en utilisant l'énergie de la lumière jaune et verte du spectre visible ; d'autres ions halogène et des nitrate NO3– sont également pompés à l'intérieur de la cellule par cette protéine. La bactériorhodopsine, quant à elle, est une autre protéine transmembranaire des halobactéries, qui pompe les protons hors des cellules sous l'effet de la lumière en vue de (fr)
- Halorodopsyna – jest integralnym białkiem błonowym występującym u halobakterii należących do domeny archeowców. Ma zdolność przenoszenia przez błonę komórkową pod wpływem światła jonów chlorkowych lub protonów. Przy oświetlaniu światłem zielonym halorodopsyna przenosi przez błonę jony chlorkowe, a przy dodatkowym oświetleniu światłem niebieskim zamienia się w pompę protonową. Działanie halorodopsyny prowadzi do wytworzenia różnicy pH w poprzek błony. Energia gradientu elektrochemicznego wykorzystywane jest następnie do syntezy ATP. (pl)
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| - Halorhodopsin is a , specific for chloride ions, found in archaea, known as halobacteria. It is a seven-transmembrane retinylidene protein from microbial rhodopsin family. It is similar in tertiary structure (but not primary sequence structure) to vertebrate rhodopsins, the pigments that sense light in the retina. Halorhodopsin also shares sequence similarity to channelrhodopsin, another light-driven ion channel. Halorhodopsin contains the essential light-isomerizable vitamin A derivative all-trans-retinal. Due to the intense attention on solving the structure and function of this molecule, halorhodopsin is one of the few membrane proteins whose crystal structure is known. Halorhodopsin uses the energy of green/yellow light to move chloride ions into the cell, overcoming the membrane potential. Beside chlorides it transports other halides and nitrates into the cell. Potassium chloride uptake by cells helps to maintain osmotic balance during cell growth. By performing the same task, light-driven anion pumps can considerably reduce the use of metabolic energy. Halorhodopsin has been the subject of much study and its structure is accurately known. Its properties are similar to those of bacteriorhodopsin, and these two light-driven ion pumps transport cations and anions in opposite directions. Halorhodopsin isoforms can be found in multiple species of halobacteria, including Halobacterium salinarum, and Natronobacterium pharaonis. Much ongoing research is exploring these differences, and using them to parse apart the photocycle and pump properties. After bacteriorhodopsin, halorhodopsin may be the best type I (microbial) opsin studied. Peak absorbance of the halorhodopsin retinal complex is about 570 nm. Just as the blue-light activated ion channel channelrhodopsin-2 opens up the ability to activate excitable cells (such as neurons, muscle cells, pancreatic cells, and immune cells) with brief pulses of blue light, halorhodopsin opens up the ability to silence excitable cells with brief pulses of yellow light. Thus halorhodopsin and channelrhodopsin together enable multiple-color optical activation, silencing, and desynchronization of neural activity, creating a powerful neuroengineering toolbox. Halorhodopsin from Natronomonas (NpHR) has been used to achieve inhibition of action potentials in neurons in mammalian systems. Since light activation of NpHR leads to an influx of chloride ions which is a part of the natural process for generating hyperpolarization, NpHR induced inhibition works very well in neurons. Original NpHR channels when expressed in mammalian cells, showed a tendency to get accumulated in the endoplasmic reticulum of the cells.To overcome the sub-cellular localization issues, an ER export motif was added to the NpHR sequence. This modified NpHR (called eNpHR2.0) was utilized successfully to drive aggregate-free, high level expression of NpHR in vivo. However, even the modified form of NpHR showed poor localization at the cell membrane. To achieve higher membrane-localization it was further modified by addition of a golgi export signal and membrane trafficking signal from a potassium channel (Kir2.1). The addition of Kir2.1 signal significantly improved the membrane localization of NpHR and this engineered form of NpHR was labeled eNpHR3.0 (en)
- L'halorhodopsine est une protéine transmembranaire formant un canal ionique spécifique aux anions chlorure Cl– chez une classe d'archées particulière appelée Halobacteria. Sa structure est semblable à celle de la bactériorhodopsine, et elle utilise également le rétinal comme cofacteur photosensible. Le pic d'absorption du complexe rétinal-halorhodopsine se situe autour de 570 nm. Ce canal pompe les ions Cl– vers l'intérieur de la cellule en utilisant l'énergie de la lumière jaune et verte du spectre visible ; d'autres ions halogène et des nitrate NO3– sont également pompés à l'intérieur de la cellule par cette protéine. La bactériorhodopsine, quant à elle, est une autre protéine transmembranaire des halobactéries, qui pompe les protons hors des cellules sous l'effet de la lumière en vue de produire de l'énergie métabolique (ATP). (fr)
- Halorodopsyna – jest integralnym białkiem błonowym występującym u halobakterii należących do domeny archeowców. Ma zdolność przenoszenia przez błonę komórkową pod wpływem światła jonów chlorkowych lub protonów. Przy oświetlaniu światłem zielonym halorodopsyna przenosi przez błonę jony chlorkowe, a przy dodatkowym oświetleniu światłem niebieskim zamienia się w pompę protonową. Jej budowa zbliżona jest do bakteriorodopsyny. Sekwencja aminokwasów w tych białkach pokrywa się w 30%. Także struktura oraz mechanizm działania zbliżony jest do bakteriorodopsyny pełniącej jedynie funkcję pompy protonowej. Zmiana we właściwościach, polegająca na nabyciu zdolności do przenoszenia jonów chlorkowych, powstała prawdopodobnie w wyniku zamiany w bakteriorodopsynie asparaginianu w pozycji 85 na treoninę. Działanie halorodopsyny prowadzi do wytworzenia różnicy pH w poprzek błony. Energia gradientu elektrochemicznego wykorzystywane jest następnie do syntezy ATP. (pl)
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