Canle iónica regulada por voltaxe: Diferenzas entre revisións

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== Estrutura ==
 
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{{further|Cation channel superfamily}}
[[Ficheiro:Ion channel in conformation.png|miniatura|Conformación de catro dominios homólogos mostrando a formación do poro central.]]
Voltage-gatedAs ioncanles channelsiónicas arereguladas generallypor composedvoltaxe ofestán severalxeralmente subunitscompostas arrangedpor invarias suchsubunidades aarranxadas wayde thattal theremaneira isque ahai un poro central porea throughtravés whichdo ionscal canpoden travelpasar downos theirións a favor do [[electrochemicalgradiente gradientelectroquímico]]s. TheAs channelscanles tendadoitan toser beespecíficas ion-specificde ión, althoughaínda similarlyque sizedos andións chargedde ionssimilar maytamaño sometimese travelcarga throughpoden them.ás Theveces functionalitypasar oftamén voltage-gateda iontravés channelsdeles. isA attributedfuncionalidade todas itscanles threeiónicas mainreguladas discretepor units:voltaxe theatribúese voltageás súas tres subunidades: o sensor de voltaxe, theo poreporo orou conductingvía pathwaycondutora, ande thea gatecomporta.<ref name="Bezanilla_2005">{{cite journal | vauthors = Bezanilla F | title = Voltage-gated ion channels | journal = IEEE Transactions on NanoBioscience | volume = 4 | issue = 1 | pages = 34–48 | date = March 2005 | pmid = 15816170 | doi=10.1109/tnb.2004.842463}}</ref> As canles de Na<sup>+</sup>, K<sup>+</sup>, ande Ca<sup>2+</sup> channelsestán arecompostas composedpor ofcatro fourdominios transmembranetransmembrana domainsdispostos arrangedarredor arounddo aporo central pore; theseestes fourcatro domainsdominios areforman partparte ofdunha asoa singlesubunidade α-subunit inno thecaso caseda ofmaioría das canles mostde Na<sup>+</sup> ande Ca<sup>2+</sup> channels, whereasmentres thereque arehai fourcatro subunidades α-subunits, eachcada contributingunha onedas transmembranecales domaincontribúe cun dominio transmembrana, inna mostmaioría das canles de K<sup>+</sup> channels.<ref name="MCB_2000">{{cite book | first1 = Harvey | last1 = Lodish | first2 = Arnold | last2 = Berk | first3 = S Lawrence | last3 = Zipursky | first4 = Paul | last4 = Matsudaira | first5 = David | last5 = Baltimore | first6 = James | last6 = Darnell | name-list-format = vanc | title = Molecular Cell Biology | date = 2000 | publisher = Scientific American Books | location = New York | isbn = 978-0-7167-3136-8 | edition = 4th | chapter = Section 21.3, Molecular Properties of Voltage-Gated Ion Channels | chapter-url = https://www.ncbi.nlm.nih.gov/books/NBK21608/ }}</ref> Os Thesegmentos membrane-spanningque segmentsse estenden dun lado a outro da membrana, designateddesignados como S1- a S6, allteñen taketodos theforma form ofde [[alphahélice helix|alpha helicesalfa]] withcon specializedfuncións functionsespecializadas. TheOs fifthquinto ande sixthsexto transmembranesegmentos segmentstransmembrana (S5 ande S6) ande poreo loopbucle servedo theporo desempeña o principal rolepapel ofna ioncondción de conductionións, comprisingcomprendendo thea gatecomporta ande poreo ofporo theda channelcanle, whilementres que S1-S4 servefuncionan ascomo therexión voltage-sensingsensible a regionvoltaxe.<ref name="Bezanilla_2005" /> TheAs fourcatro subunitssubunidades maypoden beser identicalidénticas, orou differentdiferentes fromunha one anotherdoutra. InAdemais additiondas tocatro thesubunidades fourα central α-subunitscentrais, therehai aretamén alsosubunidades regulatoryβ β-subunitsreguladoras, withcon actividade de [[oxidoreductaseoxidorreductase]] activity, whichque areestán locatedlocalizadas onna thesuperficie innerinterna surfaceda ofmembrana thecelular celle membranenon andcruzan doa notmembrana, crosse theos membrane,cales andson whichcoensamblados arecoas coassembled with thesubunidades α-subunits in theno [[endoplasmicretículo reticulumendoplasmático]].<ref>{{cite journal | vauthors = Gulbis JM, Mann S, MacKinnon R | title = Structure of a voltage-dependent K<sup>+</sup> channel beta subunit | journal = Cell | volume = 97 | issue = 7 | pages = 943–52 | date = June 1999 | pmid = 10399921 | doi=10.1016/s0092-8674(00)80805-3}}</ref>
 
== Mecanismo ==
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[[x-ray crystallography|Crystallographic]] structural studies of a [[potassium channel]] have shown that, when a [[potential difference]] is introduced over the membrane, the associated [[electric field]] induces a conformational change in the potassium channel. The conformational change distorts the shape of the channel proteins sufficiently such that the cavity, or channel, opens to allow influx or efflux to occur across the membrane. This movement of ions down their concentration gradients subsequently generates an electric [[current (electricity)|current]] sufficient to depolarize the cell membrane.