>TIGR01342 acon_putative aconitate hydratase, putative; InterPro: IPR006250 Aconitase (aconitate hydratase; 4.2.1.3 from EC) is an iron-sulphur protein that contains a [4Fe-4S]-cluster and catalyses the interconversion of isocitrate and citrate via a cis-aconitate intermediate. Aconitase functions in both the TCA and glyoxylate cycles, however unlike the majority of iron-sulphur proteins that function as electron carriers, the [4Fe-4S]-cluster of aconitase reacts directly with an enzyme substrate. In eukaryotes there is a cytosolic form (cAcn) and a mitochondrial form (mAcn) of the enzyme. In bacteria there are also 2 forms, aconitase A (AcnA) and B (AcnB). Several aconitases are known to be multi-functional enzymes with a second non-catalytic, but essential function that arises when the cellular environment changes, such as when iron levels drop , . Eukaryotic cAcn and mAcn, and bacterial AcnA have the same domain organisation, consisting of three N-terminal alpha/beta/alpha domains, a linker region, followed by a C-terminal 'swivel' domain with a beta/beta/alpha structure (1-2-3-linker-4), although mAcn is small than cAcn. However, bacterial AcnB has a different organisation: it contains an N-terminal HEAT-like domain, followed by the 'swivel' domain, then the three alpha/beta/alpha domains (HEAT-4-1-2-3) . Below is a description of some of the multi-functional activities associated with different aconitases. Eukaryotic mAcn catalyses the second step of the mitochondrial TCA cycle, which is important for energy production, providing high energy electrons in the form of NADH and FADH2 to the mitochondrial oxidative phosphorylation pathway . The TCA cycle also provides precursors for haem and amino acid production. This enzyme has a second, non-catalytic but essential role in mitochondrial DNA (mtDNA) maintenance: mAcn acts to stabilise mtDNA, forming part of mtDNA protein-DNA complexes known as nucleoids. mAcn is thought to reversibly model nucleoids to directly influence mitochondrial gene expression in response to changes in the cellular environment. Therefore, mAcn can influence the expression of components of the oxidative phosphorylation pathway encoded in mtDNA. Eukaryotic cAcn enzyme balances the amount of citrate and isocitrate in the cytoplasm, which in turn creates a balance between the amount of NADPH generated from isocitrate by isocitrate dehydrogenase with the amount of acetyl-CoA generated from citrate by citrate lyase. Fatty acid synthesis requires both NADPH and acetyl-CoA, as do other metabolic processes, including the need for NADPH to combat oxidative stress. The enzymatic form of cAcn predominates when iron levels are normal, but if they drop sufficiently to cause the disassembly of the [4Fe-4S]-cluster, then cAcn undergoes a conformational change from a compact enzyme to a more open L-shaped protein known as iron regulatory protein 1 (IRP1; or IRE-binding protein 1, IREBP1) , . As IRP1, the catalytic site and the [4Fe-4S]-cluster are lost, and two new RNA-binding sites appear. IRP1 functions in the post-transcriptional regulation of genes involved in iron metabolism - it binds to mRNA iron-responsive elements (IRE), 30-nucleotide stem-loop structures at the 3' or 5' end of specific transcripts. Transcripts containing an IRE include ferritin L and H subunits (iron storage), transferrin (iron plasma chaperone), transferrin receptor (iron uptake into cells), ferroportin (iron exporter), mAcn, succinate dehydrogenase, erythroid aminolevulinic acid synthetase (tetrapyrrole biosynthesis), among others. If the IRE is in the 5'-UTR of the transcript (e.g. in ferritin mRNA), then IRP1-binding prevents its translation by blocking the transcript from binding to the ribosome. If the IRE is in the 3'-UTR of the transcript (e.g. transferrin receptor), then IRP1-binding protects it from endonuclease degradation, thereby prolonging the half-life of the transcript and enabling it to be translated . IRP2 is another IRE-binding protein that binds to the same transcripts as IRP1. However, since IRP1 is predominantly in the enzymatic cAcn form, it is IRP2 that acts as the major metabolic regulator that maintains iron homeostasis . Although IRP2 is homologous to IRP1, IPR2 lacks aconitase activity, and is known only to have a single function in the post-transcriptional regulation of iron metabolism genes . In iron-replete cells, IRP2 activity is regulated primarily by iron-dependent degradation through the ubiquitin-proteasomal system. Bacterial AcnB is also known to be multi-functional. In addition to its role in the TCA cycle, AcnB was shown to be a post-transcriptional regulator of gene expression in Escherichia coli and Salmonella enterica , . In S.enterica, AcnB initiates a regulatory cascade controlling flagella biosynthesis through an interaction with the ftsH transcript, an alternative RNA polymerase sigma factor. This binding lowers the intracellular concentration of FtsH protease, which in turn enhances the amount of RNA polymerase sigma32 factor (normally degraded by FtsH protease), and sigma32 then increases the synthesis of chaperone DnaK, which in turn promotes the synthesis of the flagellar protein FliC. AcnB regulates the synthesis of other proteins as well, such as superoxide dismutase (SodA) and other enzymes involved in oxidative stress. This entry represents a small family of proteins homologous and likely functionally equivalent to aconitase 1. Members are found, so far in the anaerobe Clostridium acetobutylicum, in the microaerophilic, early-branching bacterium Aquifex aeolicus, and in the halophilic archaeon Halobacterium sp. NRC-1. No member is experimentally characterised. More information about these proteins can be found at Protein of the Month: Aconitase ..

Probab=100.00 E-value=0 Score=1252.94 Aligned_cols=642 Identities=31% Similarity=0.498 Sum_probs=539.8 Q ss_pred CCCHHHHHHHHHCCCCCCCCCCCCCCCCCHHHEECCCCHHHHHHHHHHHHHHHHCCCCHHHCCCCCCEEEE---EECC-C Q ss_conf 57999999986123554577766364532522000003579999999999999719999992878981399---8683-2 Q gi|254780451|r 59 TVTKEQIHAFVKWLDNKGTVESEVSYRFSRVLMQDFTGVPAVVDLAAMRDAIVVLGGDPQNINPLVPVDLV---IDHS-L 134 (896) Q Consensus 59 ~~~~~~~~~~~~w~~~~~~~~~ei~f~p~Rv~~qD~Tg~pa~vdlaamR~~~~~~g~dp~~inp~vp~dlv---iDHs-v 134 (896) T Consensus 1 T~~~KI~~~HL--V~G~l~PGEEI~I~IDQTL~QD~TGTM~yL~FEAl-------~~------~EV~TEL~~~Y~DH~~~ 65 (658) T TIGR01342 1 TLAEKILDDHL--VEGDLEPGEEIAIKIDQTLSQDATGTMVYLEFEAL-------EV------DEVKTELAVSYIDHNTL 65 (658) T ss_pred CCHHHEHHCCE--ECCCCCCCCEEEEEECCCCCCCCCCEEEEEEEEEC-------CC------CHHHHEEEEEEECCCHH T ss_conf 90232212001--21557887235357535225676530677764313-------78------50001000000012001 Q ss_pred HHHCCCCHHHHHHHHHHHHHHHHHHHHHHHHHHHHCCCEEEECCCCCCHHHHHHHHHCCCEEEECCCCCEEEEEE-EEEE Q ss_conf 110059988999899988754267899998774214880786088762167789863351131036886179830-1320 Q gi|254780451|r 135 IVDYSGNKDAVTRNKDLEYQRNEERYRFLKWGQKSFKNFRVVPPGTGICHQINLEYLGQSVWTKNENGENIAYPD-TCVG 213 (896) Q Consensus 135 ~vd~~g~~~a~~~n~~~e~~rN~Ery~Flkwa~~~f~~~~v~pPG~GI~HQvnlE~la~vv~~~~~~~~~~a~Pd-tlVG 213 (896) T Consensus 66 Q~DF----------------~N~DDH~yL~S~A~~y-G~ylS~PGNGICH~VH~E~--------------FA~PGKTLLG 114 (658) T TIGR01342 66 QFDF----------------KNADDHKYLRSVAKKY-GIYLSKPGNGICHNVHKER--------------FAKPGKTLLG 114 (658) T ss_pred CCCC----------------CCCCHHHHHHHHHHHC-CEEEECCCCCCCCCCCCHH--------------CCCCCCCCCC T ss_conf 0234----------------4452147999865215-7257468796322313020--------------1788772036 Q ss_pred CCCCCCCCCCCHHHHCCCCHHHHHHHHCCCCCEECCCCEEEEEEECCCCCCCCHHHHHHHHHHHHCCCCCCCEEEEEEEC Q ss_conf 68876444520123203434899999707751411672899999767786443688999999984102212127999615 Q gi|254780451|r 214 TDSHTTMINALGILGWGVGGIEAEAAMLGCPISMLLPEVVGFEVTGSLQEGVTATDLVLTITQMLRKEGVVSKFVEFFGS 293 (896) Q Consensus 214 tDSHT~~~galG~la~GVGg~eaea~mlGqp~~~~vPevigv~L~G~L~~gVtakDiiL~i~~~Lr~~Gvvgk~vEf~G~ 293 (896) T Consensus 115 SDSHTPT~GGlG~LAIGAGG~D~A~AM~G~~yY~~MP~~V~V~L~G~lPEW~TAKD~ILELLRRL~VKGG~GK~lEY~G~ 194 (658) T TIGR01342 115 SDSHTPTAGGLGQLAIGAGGLDVAVAMAGEAYYLKMPKVVNVRLKGKLPEWVTAKDVILELLRRLSVKGGLGKVLEYFGE 194 (658) T ss_pred CCCCCCCCCCCCHHHHCCCHHHHHHHHCCCCEEEECCEEEEEEECCCCCCCCCHHHHHHHHHHHHEECCCCCEEEEECCC T ss_conf 67788888653304122551687865078823742780887786155885201689999987650002675216752188 Q ss_pred CCCCCCHHHHHHHHCCCCCCCCCEEEECCCHHHHHHHHHCCCCHHHHHHHHHHHHHHHCCCCCCCCCCCCCCEEEEEECC Q ss_conf 50017875632120001003720377519989999998639998899999987464102367676678863069999803 Q gi|254780451|r 294 GFESMVLADRATIANMAPEYGATCGFFPVDRGTIDYLRLSGRSNSRVDLVEAYTKVQGMWREDIDYEKVAFTKKMKLDLG 373 (896) Q Consensus 294 gi~~LS~~dRaTIaNMa~E~GAt~gifp~De~T~~YL~~tGR~~~~v~lve~Y~ka~~l~~~~~~d~~a~Y~~vieiDLs 373 (896) T Consensus 195 GV~~LSVPER~TITNMG~ELGAT~SIFP~D~~T~~yL~~~~RE~~~V~L--------------~~D~DAEY~~~I~~~LS 260 (658) T TIGR01342 195 GVKELSVPERATITNMGAELGATSSIFPSDDITRDYLAAFDREDDFVDL--------------LADADAEYDDVIVVDLS 260 (658) T ss_pred CCCCCCCCCCCCHHHCCHHHCCCCCCCCCHHHHHHHHHHCCCCHHHHHC--------------CCCCCCCCCCEEEEECC T ss_conf 7120368863220102421324444578716799999850770024422--------------78898753466788302 Q ss_pred CCCCHHCCCCCCCCEEEHHHHHHHHHHHHHHHCCCHHHHHHHCCCCCCCCCCCCCCEEEEEEECCCCCCCHHHHHHHHHH Q ss_conf 14301226566564136777301166876640011002321024578888875554457531046765459998778899 Q gi|254780451|r 374 NVSPSVAGPRRPESRLSLSEVPSSFVTEMNEYYKKSHTLDEKYPVKGCDFHLKHGDVAIASITSCTNTFNPSVMIGAGLL 453 (896) Q Consensus 374 ~ieP~VAgP~~P~d~v~l~~v~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~l~~g~VvIAaIgSCTNtSnp~~miaAgll 453 (896) T Consensus 261 ~LEPLIA~P~~PDNVVPVRE~~G-------------~~V~------------------QV~~GSCTN~~y~D~~~AAKlL 309 (658) T TIGR01342 261 DLEPLIAEPSSPDNVVPVREVEG-------------IKVD------------------QVVVGSCTNSAYVDLLRAAKLL 309 (658) T ss_pred CCCCCCCCCCCCCCCCCCEEECC-------------EEEE------------------EEEEEECCCCHHHHHHHHHHHH T ss_conf 47852257663687111022057-------------0761------------------3888501462077788776651 Q ss_pred HHHHHHCCCCCCCCCEEEEECCCHHHHHHHHHCCCHHHHHHHCCEECCCCCCCCCCCCCCCCCHHHHHCCCCCEEEEEEE Q ss_conf 98898649875867307970161899999998588577775053020553224212777688302210113663587863 Q gi|254780451|r 454 ARNAVRAGLKSKPWVKTSCAPGSQVSYEYLVQAGLVEYLEALGFSLVGFGCTTCIGNSGALKKEISEVIHQKSLVVAGVL 533 (896) Q Consensus 454 AkkAv~~Glkv~p~Vkt~l~PGS~~V~~~L~~~Gll~~L~~aGf~i~~~GCg~CiGnsG~l~~~i~~~i~~~~l~~~sV~ 533 (896) T Consensus 310 ------EGR~V~~~~~~~VAPGSKQA~El~~~~G~~~~~l~AG~~~~E~~CG~CIG~-G~~P~~~----------~VS~R 372 (658) T TIGR01342 310 ------EGRRVSKDVVFIVAPGSKQALELLAREGALLEFLKAGVRILEAACGACIGI-GFVPASD----------SVSLR 372 (658) T ss_pred ------CCCEECCCEEEEECCCCHHHHHHHHHCCHHHHHHHHHHHHHHHCCCCCCCC-CCCCCCC----------CEEEE T ss_conf ------486425752799758855789997504468999884045544227851034-3217998----------55641 Q ss_pred CCCCCCCCCCCCCCCCEEECCHHHHHHHHHHCCCCCCCCCCCCCC-CCCCCCCCCCCC-CCCHHHHHHHHHHHCCCCCCC Q ss_conf 367666654685433100059789999985161222310023554-888863200156-888578888876415832100 Q gi|254780451|r 534 SGNRNFEGRISPDVEANYLLSPPLVVAYALAGNVRKNLIKDPIGE-DQQGSPVYLRDI-WPKDSEIQSFVNKYVTCDLYK 611 (896) Q Consensus 534 SgNRNFeGR~~p~~~~~yLaSP~lVvA~AiaG~I~~d~~~dplg~-~~~G~~v~L~Di-wPs~~Ei~~~~~~~v~~~~f~ 611 (896) T Consensus 373 ~FNRNF~GR~G~~D~~VYL~SPE~~~A~AIAGEI-----~DPR~L~~~~G------d~~~~~----------~EM~~~y~ 431 (658) T TIGR01342 373 SFNRNFKGRAGIEDDKVYLASPEVAVAAAIAGEI-----VDPRDLADDLG------DLKAIR----------VEMGEKYS 431 (658) T ss_pred EECCCCCCCCCCCCCCEEECCHHHHHHHHHHCCC-----CCCHHHHHCCC------CEEEEE----------EECCCCCC T ss_conf 1045677888887670674270589898761565-----37355541048------624422----------10687688 Q ss_pred CCCCCCCCCCHHHCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCEEEEEECCCCCHHHCCCCCCCCCCC Q ss_conf 01223347871220155787762056743334237887677654554332435855899965885723316456555447 Q gi|254780451|r 612 KKYSDVFKGDSSWWNIEVPESETYMWDEKSTYVRNPPYFETISKHIPEIVDICGARILCLLGDKITTDHISPAGSIPLQS 691 (896) Q Consensus 612 ~~y~~i~~g~~~w~~l~~~~~~~y~w~~~StyI~~pPff~~~~~~~~~~~~i~~arvL~~lGD~iTTDHISPAG~I~~~s 691 (896) T Consensus 432 ~Gy~~~~~------~~~~~E-E-----~~~~~~~~GPNI~~~P~~~PL~~~~~G-E~~L~~~DNITTDHI~PA~~----- 493 (658) T TIGR01342 432 YGYDEADI------DILTKE-E-----RIDVDLIKGPNIKSLPVKDPLGEDVRG-EVLLKVEDNITTDHIIPATA----- 493 (658) T ss_pred CCCCCCCC------CCCCCC-C-----CCCCCEECCCCCCCCCCCCCCCCCCCE-EEEEEEECCCCCCCCCCCCC----- T ss_conf 87676667------888854-4-----545330018688648886868885210-18899715765253256641----- Q ss_pred CHHHHHHHCCCCHHHHHHHHHHCCCHHHHHHHHHCCCHHHHHHCCCCCCCCCCEEECCCCCEEEHHHHHHHHHHCCCCEE Q ss_conf 37888987498865631456530235777665203601223212577765772245389978737999998998199889 Q gi|254780451|r 692 AAASYLRQRGVKEKDFNQFGTRRGNHEVMMRGTFSNIRICNYMLGEEGKKGGYTIHYPSKEELFIYDAAMRYKVDQVPLV 771 (896) Q Consensus 692 pAg~yL~~~Gv~~~dfNsygsRRgNhevM~RGtFaNirl~N~l~~~~~~egg~T~~~p~~~~~~iydaA~~Y~~~~~plV 771 (896) T Consensus 494 ---~IL~lR--------------SNI~~~-------------------SE--y~~~~~D~~---F~~R~K~~~~kGkaG~ 532 (658) T TIGR01342 494 ---DILKLR--------------SNIEAL-------------------SE--YVLSRVDDE---FVERAKKLDEKGKAGV 532 (658) T ss_pred ---CHHHHH--------------HHHHHH-------------------HH--HHHHHCCHH---HHHHHHHHHHCCCEEE T ss_conf ---011013--------------457887-------------------55--754202735---7899998750587348 Q ss_pred EECCCCCCCCCHHHHHHHHHHHCCEEEEEECCHHHHHHHCCCCCEEEEEECCCCCCHHHHCCCCCEEEEEEC--HHHCCC Q ss_conf 994677786730799988667617089997647898885053552322331789898881989743899726--322589 Q gi|254780451|r 772 VFAGVEYGNGSSRDWAAKGTRLLGVRSVIAESFERIHRSNLIGMGVIPFAFGKGISWKNLNIKGDEIINIRK--LKTISP 849 (896) Q Consensus 772 ViAG~~YG~GSSRdwAAkgp~lLGVkAVIA~SFeRIHrsNLv~mGiLPL~F~~~~~~~~L~l~G~E~~~i~~--~~~l~p 849 (896) T Consensus 533 ~~~GENYGQGSSREHAAl~P~FLGV~~V~A~SFARIH~ANL~NFG~~PL~~~n~E~Y~~~~-~GD~-~E~~~d~~~~~~~ 610 (658) T TIGR01342 533 LVAGENYGQGSSREHAALAPRFLGVRAVLAKSFARIHKANLVNFGVLPLEIDNKEDYDKIE-LGDD-VEVVDDLIEALKD 610 (658) T ss_pred EECCCCCCCCCCHHHHHHCCHHHHHHHHHHHHHHHHHHHHHHCCCEEECCCCCCCCHHHHC-CCCC-EECHHHHHHHHHC T ss_conf 9735447888644688627512106888877676665430000220002246743446541-7981-3226899899847 Q ss_pred CCEEEEEEEECCCCEEEEEEEEEECCHHHHHHHHCCCHHHHHHHH Q ss_conf 973899998189967999999873899999999909836898887 Q gi|254780451|r 850 RQESTLEIHYSDGTFKCVPIICCIDTLDEINHLKNGGILQAVLRQ 894 (896) Q Consensus 850 ~~~v~v~i~~~~g~~~~~~~~~r~dt~~E~~~~~~GGiL~yvlr~ 894 (896) T Consensus 611 G~~~-l~~~~~~~--~E~~~T~~~-~~~~~~~L~AGG~L~~~K~~ 651 (658) T TIGR01342 611 GEDI-LVVRKTDD--EEILATLDL-SEVEKRILIAGGKLSLIKNK 651 (658) T ss_pred CCEE-EEEEECCC--CEEEEEECC-CHHHHHHEECCCCHHHHHHH T ss_conf 9748-99973488--436654047-83221210017601112201

HHsearch alignment for GI: 254780451 and conserved domain: TIGR01342