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ArsB And ArsAB Transporters
Arsenite resistance (Ars) efflux pumps of bacteria may consist of two proteins, ArsBTC# 2.A.45.1.1 the integral membrane constituent with twelve transmembrane spanners) and ArsATC# 3.A.4.1.1 the ATP-hydrolyzing, transport energizing subunit, as for the chromosomally-encoded ''E. coli'' system), or of one protein (just the ArsB integral membrane protein of the plasmid-encoded ''Staphylococcus'' system). ArsA proteins have two ATP binding domains and probably arose by a tandem gene duplication event. ArsB proteins all possess twelve transmembrane spanners and may also have arisen by a tandem gene duplication event. Structurally, the Ars pumps resemble ABC-type efflux pumps, but there is no significant sequence similarity between the Ars and ABC pumps. When only ArsB is present, the system operates by a pmf-dependent mechanism, and consequently belongs in TC subclass 2.A (i.eTC# 2.A.45. When ArsA is also present, ATP hydrolysis drives efflux, and consequently the system belongs in T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arsenite
In chemistry, an arsenite is a chemical compound containing an arsenic oxyanion where arsenic has oxidation state +3. Note that in fields that commonly deal with groundwater chemistry, arsenite is used generically to identify soluble AsIII anions. IUPAC have recommended that arsenite compounds are to be named as arsenate(III), for example ortho-arsenite is called trioxidoarsenate(III). Ortho-arsenite contrasts to the corresponding anions of the lighter members of group 15, phosphite which has the structure and nitrite, which is bent. A number of different arsenite anions are known: * ortho-arsenite, an ion of arsenous acid, with a pyramidal shape * meta-arsenite, a polymeric chain anion. * pyro-arsenite, * a polyarsenite, * a polyarsenite, *, a polymeric anion In all of these the geometry around the AsIII centers are approximately trigonal, the lone pair on the arsenic atom is stereochemically active. Well known examples of arsenites include sodium meta-arsenite which contai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exodermis
The exodermis is a physiological barrier that has a role in root function and protection. The exodermis is a membrane of variable permeability responsible for the radial flow of water, ions, and nutrients. It is the outer layer of a plant's cortex. The exodermis serves a double function as it can protect the root from invasion by foreign pathogens and ensures that the plant does not lose too much water through diffusion through the root system and can properly replenish its stores at an appropriate rate. Overview and function The exodermis is a specialized type of hypodermis that develops Casparian strips in its cell wall, as well as further wall modifications. The Casparian strip is a band of hydrophobic, corky-like tissue that is found on the outside of the endodermis and the exodermis. Its main function is to prevent solution backflow into the cortex and to maintain root pressure. It is also involved in ensuring that soil is not pulled directly into the root system duri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Transport
In cellular biology, ''active transport'' is the movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. Active transport requires cellular energy to achieve this movement. There are two types of active transport: primary active transport that uses adenosine triphosphate ( ATP), and secondary active transport that uses an electrochemical gradient. Some examples of active transport include: * Phagocytosis of bacteria by macrophages * Movement of calcium ions out of cardiac muscle cells * Transportation of amino acids across the intestinal lining in the human gut * Secretion of proteins such as enzymes, peptide hormones, and antibodies from various cells * Functioning of white blood cells to defend invading diseases Active cellular transportation (ACT) Unlike passive transport, which uses the kinetic energy and natural entropy of molecules moving down a gradient, active ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arsenite-transporting ATPase
In enzymology, an arsenite-transporting ATPase () is an enzyme that catalyzes the chemical reaction :ATP + H2O + arsenitein \rightleftharpoons ADP + phosphate + arseniteout The 3 substrates of this enzyme are ATP, H2O, and arsenite, whereas its 3 products are ADP, phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phospho ..., and arsenite. This enzyme belongs to the family of hydrolases, specifically those acting on acid anhydrides acting on acid anhydrides to catalyse transmembrane movement of substances. The systematic name of this enzyme class is ATP phosphohydrolase (arsenite-exporting). Structural studies As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes , , and . See also * Arsenite-Antimonite efflux Reference ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arsenite-Antimonite Efflux
Arsenite-antimonite transporters are membrane transporters that pump arsenite or antimonite out of a cell. Antimonite is the salt of antimony (Sb(III)) and has been found to significantly impact the toxicity of arsenite. The similar structure of As(III) and Sb(III) makes it plausible that certain transporters function in the efflux of both substrates. Arsenic efflux transporters exist in almost every organism and serve to remove this toxic compound from the cell. Subfamilies As of early 2016, there are at least three known families of proteins known to participate in arsenite and antimonite efflux. * ArsB familyTC# 2.A.45 * ArsAB FamilyTC# 3.A.4 * Arsenical resistance-3 (ARC3) familyTC#2.A.59 The membrane transporter ArsB can function as a secondary carrier or as a primary active transporter, in which case ArsA, an ATPase, must be superimposed onto ArsB. Arsenite and antimonite can also be pumped out of the cell by members of the ARC3 family, a member of the BART superfami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ARC3 Family
The arsenical resistance-3 (ACR3) familyTC# 2.A.59 is a member of the BART superfamily. Based on operon analyses, ARC3 homologues may function either as secondary carriers or as primary active transporters, similarly to the ArsB and ArsAB families. In the latter case ATP hydrolysis again energizes transport. ARC3 homologues transport the same anions as ArsA/AB homologues, though ArsB homologues are members of the IT Superfamily and homologues of the ARC3 family are within the BART Superfamily suggesting they may not be evolutionarily related. Structure and Homology ''Bacillus'' ARC3 (ArsBTC# 2.A.59.1.2 probably has a 10 TMS topology. ACR3 of ''S. cerevisiae'' is 404 amino acyl residues long and exhibits 10 putative transmembrane α-helical spanners (TMSs). Homologues are found in ''Mycobacterium tuberculosis'' (498 aas; gbZ80225), ''Archaeoglobus fulgidus'' (370 aas; gbAE001071), '' Methanobacterium thermoautotrophicum'' (365 aas; gbAE000865) and ''Synechocystis'' (383 aas; sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ion Transporter Superfamily
The ion transporter (IT) superfamily is a protein superfamily, superfamily of secondary carriers that transport proteins, transport charged substrates. Families As of early 2016, the currently recognized and functionally defined families that make up the IT superfamily include: 2.A.8- Gluconate-Proton symporter, The Gluconate:H+ Symporter (GntP) Family 2.A.11- Citrate symporter, The Citrate-Mg2+:H+ (CitM) Citrate-Ca2+:H+ (CitH) Symporter (CitMHS) Family 2.A.13- C4-dicarboxylate uptake, The C4-Dicarboxylate Uptake (Dcu) Family 2.A.14- Lactate permease, The Lactate Permease (LctP) Family 2.A.34- NhaB family, The NhaB Na+:H+ Antiporter (NhaB) Family 2.A.35- NhaC family, The NhaC Na+:H+ Antiporter (NhaC) Family 2.A.45- ArsB and ArsAB transporters, The Arsenite-Antimonite (ArsB) Efflux Family 2.A.47- Divalent anion-Sodium symporter, The Divalent Anion:Na+ Symporter (DASS) Family 2.A.61- DcuC family, The C4-dicarboxylate Uptake C (DcuC) Family 2.A.62- NhaD family, The NhaD Na+:H+ Anti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antimonite
In chemistry, antimonite refers to a salt of antimony(III), such as NaSb(OH)4 and NaSbO2 (meta-antimonite), which can be prepared by reacting alkali with antimony trioxide, Sb2O3.Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier These are formally salts of antimonous acid, Sb(OH)3, whose existence in solution is dubious. Attempts to isolate it generally form Sb2O3·''x''H2O, antimony(III) oxide hydrate, which slowly transforms into Sb2O3. In geology, the mineral stibnite, Sb2S3, is sometimes called antimonite. Antimonites can be compared to antimonate In chemistry an antimonate is a compound which contains a metallic element, oxygen, and antimony in an oxidation state of +5. These compounds adopt polymeric structures with M-O-Sb linkages. They can be considered to be derivatives of the hypothetic ...s, which contain antimony in the +5 oxidation state. References Antimony(III) compounds Oxyanions {{inorganic-compound-stub th:สติบไ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arsenic Toxicity
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but only the gray form, which has a metallic appearance, is important to industry. The primary use of arsenic is in alloys of lead (for example, in car batteries and ammunition). Arsenic is a common n-type dopant in semiconductor electronic devices. It is also a component of the III-V compound semiconductor gallium arsenide. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, and insecticides. These applications are declining with the increasing recognition of the toxicity of arsenic and its compounds. A few species of bacteria are able to use arsenic compounds as respiratory metabolites. Trace quantities of arsenic are an essential dietary element in rats, hamsters, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protochlorophyllide Reductase
In enzymology, protochlorophyllide reductases (POR) are enzymes that catalyze the conversion from protochlorophyllide to chlorophyllide ''a''. They are oxidoreductases participating in the biosynthetic pathway to chlorophylls. There are two structurally unrelated proteins with this sort of activity, referred to as light-dependent (LPOR) and dark-operative (DPOR). The light- and NADPH-dependent reductase is part of the short-chain dehydrogenase/reductase (SDR) superfamily and is found in plants and oxygenic photosynthetic bacteria, while the ATP-dependent dark-operative version is a completely different protein, consisting of three subunits that exhibit significant sequence and quaternary structure similarity to the three subunits of nitrogenase.Yuichi Fujita and Carl E. Bauer (2000). Reconstitution of Light-independent Protochlorophyllide Reductase from Purified Bchl and BchN-BchB Subunits. J. Biol. Chem., Vol. 275, Issue 31, 23583-23588/ref> This enzyme may be evolutionary ol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
