Helicase: Diferenzas entre revisións

[[FileFicheiro:Human DEAD-box RNA helicase.jpg|thumbminiatura|rightdereita|HumanARN helicase de caixa DEAD-box RNA helicasehumana.]]

RNAAs ARN helicases areson essentialesenciais forpara mosta processesmaioría ofdos RNAprocesos metabolismdo suchmetaboiismo asdo ARN como a bioxénese de [[ribosomeribosoma]] biogenesiss, pre-mRNAo [[splicing]] anddo ARNm e a iniciación da [[translationtradución de proteínas|tradución]] initiation. TheyTamén alsodesempeñan playun animportante importantpapel rolena indetección sensingdos viralARNs RNAsvirais.<ref name="rnadatabase" /> RNAAs ARN helicases areestán involvedimplicadas inna themadiación mediationda ofresposta inmune antiviral immuneporque responsepoden becauseidentificar theyo canARN identifyalleo foreignen RNAs in vertebratesvertebrados. AboutAproximadamente o 80% ofdos allvirus virusesson are[[virus RNAde virusesARN]] ande theyconteñen containas theirsúas ownpropias RNAARN helicases.<ref name="rnavirus">{{Cite Steimer, L.; Klostermeier, D. (2012). "RNA helicases in infection and disease". RNA Biology 9 (6): 751–771. doi|:10.4161/rna.20090}}. PMID 22699555.</ref> DefectiveAs RNAARN helicases havedefectuosas beenforon linkedasociadas tocon cancerscancros, infectious[[doenzas diseasesinfecciosas]] ande neuro-degenerativetrastornos disordersneurodexenerativos.<ref name="rnadatabase" /> SomeAlgúns neurologicaltrastornos disordersneurolóxicos associatedasociados withcon defectiveARN RNAhelicases helicasesdefectuosas areson: [[amyotrophicesclerose lateral sclerosisamiotrófica]], [[spinalatrofia muscular atrophyespiñal]], [[Spinocerebellar ataxia|spinocerebellar espiñocerebelar|ataxia type-espiñocerebelar de tipo 2]], [[Alzheimerenfermidade diseasede Alzheimer]], ande [[lethalsíndrome de congenitalcontractura contractureconxénita syndromeletal]].<ref name="rnavirus" />

RNAAs ARN helicases ande DNAADN helicases canpoden beencontrarse foundxuntas togetheren intodas allas thesuperfamilias helicasede superfamilieshelicases exceptagás foren SF6.<ref name="isbn1-84755-914-X">{{cite book | editor = Jankowsky E | title = RNA Helicases (RSC Biomolecular Sciences) | publisher = Royal Society of Chemistry | location = Cambridge, England | year = 2010 | page = 5 | isbn = 1-84755-914-X | chapter = An introduction to RNA helicases: superfamilies, families, and major themes | author = Jankowsky E, Fairman-Williams ME }}</ref><ref name="rnahelicases">{{Cite Ranji, A.; Boris-Lawrie, K. (2010). "RNA helicases: Emerging roles in viral replication and the host innate response". RNA Biology 7 (6): 775–787. doi|:10.4161/rna.7.6.14249}}. PMC 3073335. PMID 21173576. </ref> AllTodas theas eukaryotic RNAARN helicases thateucariotas haveque beenforon identifiedidentificadas upata toagora datenon areforman non-ringanel forminge andson arede part oftipo SF1 andou SF2. OnPor the otheroutra handparte, ring-formingas RNAARN helicases haveque beenforman foundanel inencontráronse bacteriaen andbacterias e virusesvirus.<ref name="rnadatabase" /> HoweverPorén, notnon alltodas RNAas ARN helicases exhibitmostran actividade de helicase activitydefinida as definedpola bysúa enzymaticfunción functionencimática, i.e.é dicir, proteinsproteínas ofda thefamilia Swi/Snf family. AlthoughAínda theseque proteinsestas carryproteínas thelevan typicalos helicasemotivos motifstípicos das helicases, hydrolizehidrolizan ATP inde amaneira nucleicdependente acid-dependentde mannerácido nucleico, ande areestán builtconstruídas aroundarredor adun helicasenúcleo corede helicase, inen generalxeral, nonon se observa nelas ningunha actividade de unwindingdesenrolamento activityde isácidos observednucleicos.<ref name="pmid20813532">{{cite journal | author = Jankowsky E | title = RNA helicases at work: binding and rearranging | journal = Trends Biochem. Sci. | volume = 36 | issue = 1 | pages = 19–29 |date=January 2011 | pmid = 20813532 | pmc = 3017212 | doi = 10.1016/j.tibs.2010.07.008 }}</ref>

RNAAs ARN helicases thatque domostran exhibitunha unwindingactividade activityde havedesenrolamento beenforon characterizedcaracterizadas bypor atpolo leastmenos twodous differentmecanismos mechanismsdiferentes: canonicaldesenrolamento duplexdo unwindingdúplex andcanónico locale strandseparación separationde febras local. CanonicalO duplexdesenrolamento unwindingde isdúplex thecanónico stepwiseé directionala separationseparación ofdireccional agradual duplexdunha strandfebra dúplex, ascomo describedse abovedescribiu máis arriba, forpara o DNAdesenrolamento unwindingdo ADN. HoweverPorén, locala strandseparación separationde occursfebras bylocal aocorre processpor whereinun theproceso helicaseno enzymeque iso loadedencima athelicase anycárgase placeen alongcalquera thepunto duplex.ao Thislongo isdo usuallydúplex. aidedA byisto aaxuda single-strandunha regionrexión ofmonocatenaria thedo RNAARN, ande thea loadingcarga ofdo theencima enzymeestá isacompañada accompaniedda withunión de ATP binding.<ref name="pmid17964264">{{cite journal | author = Yang Q, Del Campo M, Lambowitz AM, Jankowsky E | title = DEAD-box proteins unwind duplexes by local strand separation | journal = Mol. Cell | volume = 28 | issue = 2 | pages = 253–63 |date=October 2007 | pmid = 17964264 | doi = 10.1016/j.molcel.2007.08.016 }}</ref> OnceUnha thevez helicaseque andestán ATPunidos areas boundhelicases e o ATP, localocorre stranda separationseparación occursde febras local, whicho requirescal bindingrequire ofa unión do ATP butpero notnon thea actualhidrólise processde ofdito ATP hydrolysis.<ref name="pmid19088201">{{cite journal | author = Liu F, Putnam A, Jankowsky E | title = ATP hydrolysis is required for DEAD-box protein recycling but not for duplex unwinding | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 105 | issue = 51 | pages = 20209–14 |date=December 2008 | pmid = 19088201 | pmc = 2629341 | doi = 10.1073/pnas.0811115106 }}</ref> PresentedPresentado withcon fewerpoucos basepares pairsde thebases duplexo thendúplex dissociatesdisóciase withoutdespois furthersen assistancenecesitar frommáis theasistencia enzymedo encima. ThisEste modemodo ofde unwindingdesenrolamento isé usedo byutilizado DEAD-boxpolas helicases de caixa DEAD.<ref name="pmid21297876">{{cite journal | author = Jarmoskaite I, Russell R | title = DEAD-box proteins as RNA helicases and chaperones | journal = Wiley Interdiscip Rev RNA | volume = 2 | issue = 1 | pages = 135–52 | year = 2011 | pmid = 21297876 | pmc = 3032546 | doi = 10.1002/wrna.50 }}</ref>

ThereHai is aunha [http://www.rnahelicase.org/ RNAbase helicasede database]datos currentlyde availableARN onlinehelicases] thatdispoñible containson aline comprehensiveque listcontén ofunha RNAlista de ARN helicases withcon informationinformación suchda assúa sequencesecuencia, structureestrutura, ande biochemicalfuncións andbioquímicas cellulare functionscelulares.<ref name=rnadatabase>{{Cite Jankowsky, A.; Guenther, U. -P.; Jankowsky, E. (2010). "The RNA helicase database". Nucleic Acids Research 39 (Database issue): D338–D341. doi|:10.1093/nar/gkq1002}}. PMC 3013637. PMID 21112871.</ref>