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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] |