Aconitase: Diferenzas entre revisións

| Name = aconitatoAconitato hidratase

InA contrastdiferenza withda themaioría majority ofdas [[ironproteína ferro-sulfursulfurada|proteínas proteinferro-sulfuradas]]s thatque functionfuncionan ascomo electrontransportadores carriersde electróns, theo [[iron-sulfur cluster de ferro-xofre]] ofda aconitase reactsreacciona directlydirectamente withco an[[substrato enzymeencimático|substrato]] substratedo encima. AconitaseA hasaconitase anten activeun ''cluster'' [Fe₄S₄]²⁺ clusteractivo, whichque mayse convertpode toconverter aná inactiveforma [Fe₃S₄]⁺ forminactiva. ThreeHai tres residuos de [[cysteinecisteína]] (Cys) residuesque havefuncionan beencomo shown to be ligands[[ligando]]s ofdo thecentro [Fe₄S₄] centre. InNo theestado active stateactivo, theo labileión [[iron]]ferro ionlábil ofdo the''cluster'' [Fe₄S₄] clusternon isestá notcoordinado coordinatedpola bycisteína Cyssenón butpor bymoléculas waterde moleculesauga.

TheSon homólogos da aconitase a [[iron-responsiveproteína element-bindingde proteinunión ao elemento de resposta ao ferro]] (IRE-BP) ande a [[3-Isopropylmalateisopropilmalato dehydratasedeshidratase|3-isopropylmalateisopropilmalato dehydratasedeshidratase]] (α-isopropylmalateisopropilmalato isomerase; {{número EC number|:4.2.1.33}}), anque enzymeé catalysingun theencima secondque stepcataliza ino thesegundo biosynthesispaso ofda biosíntese de [[leucineleucina]],. areOs known[[IRE|elementos aconitaseregulatorios homologues.do Iron regulatory elementsferro]] (IREs) constituteconstitúen aunha familyfamilia ofde [[ARN]]s de 28-nucleotide [[nucleótido]]s, non-coding codificantes, stemcon estruturas de [[talo-loopbucle]] structuresque thatregulan regulateo ironalmacenameto storagede ferro, a síntese de grupos [[hemehemo]] synthesise anda ironcaptación uptakede ferro. TheyTamén participan alsona participateunión indo [[ribosomeARNm]] binding and control theao [[mRNAribosoma]] turnovere (degradation)no control da degradación do ARNm. TheUnha specificproteína regulatorreguladora proteinespecífica, thea [[IRE-BP]], bindsúnese toaos IREs[[IRE]]s intanto bothnas rexións 5' andcoma nas 3' regions, butpero onlysó toao RNAARN inna theforma apo form, withoutsen the Fe-So ''cluster'' de ferro-xofre. ExpressionA ofexpresión da IRE-BP inen cultured[[cultivo cellscelular|células hasen revealedcultivo]] thatrevelou theque a proteinproteína functionsfunciona either as an active aconitase, when cells are iron-replete, or as an active RNA-binding protein, when cells are iron-depleted. Mutant IRE-BPs, in which any or all of the three Cys residues involved in Fe-S formation are replaced by [[serine]], have no aconitase activity, but retain RNA-binding properties.