>TIGR01340 aconitase_mito aconitate hydratase, mitochondrial; InterPro: IPR006248 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 mitochondrial aconitase (mAcn), as well as close homologues such as certain bacterial aconitase A (AcnA) enzymes. More information about these proteins can be found at Protein of the Month: Aconitase .; GO: 0003994 aconitate hydratase activity, 0051539 4 iron 4 sulfur cluster binding, 0006099 tricarboxylic acid cycle.

Probab=100.00 E-value=0 Score=1474.67 Aligned_cols=717 Identities=29% Similarity=0.441 Sum_probs=611.5 Q ss_pred CCCCCCHHHHHHHHHCCCCCCC----C------CCCCCCCCCHHHEECCCCHHHHHHHHHHHHHHHHCCCCHHHCCCCCC Q ss_conf 8665799999998612355457----7------76636453252200000357999999999999971999999287898 Q gi|254780451|r 56 DGCTVTKEQIHAFVKWLDNKGT----V------ESEVSYRFSRVLMQDFTGVPAVVDLAAMRDAIVVLGGDPQNINPLVP 125 (896) Q Consensus 56 ~~~~~~~~~~~~~~~w~~~~~~----~------~~ei~f~p~Rv~~qD~Tg~pa~vdlaamR~~~~~~g~dp~~inp~vp 125 (896) T Consensus 18 ~pLTlaEKiLYSHLddp~~S~~S~d~~Gr~~RG~~yLkL~PDRVamQDA~AQMAlLQFm~~-----------gL~~~~~P 86 (761) T TIGR01340 18 RPLTLAEKILYSHLDDPEESLLSQDISGRDVRGKSYLKLRPDRVAMQDASAQMALLQFMTA-----------GLPQVAVP 86 (761) T ss_pred CCCHHHHHHHHHCCCCHHHCEEECCCCCCEECCCCCCCCCCCCCCCCCHHHHHHHHHHHHC-----------CCCCCCCC T ss_conf 9722555556420467202303024565322145454448860001036789999999865-----------88887646 Q ss_pred EEEEEECCCHHHCCCCHHHHHHHHHHHHHHHHHHHHHHHHHHHHCCCEEEECCCCCCHHHHHHHHHCCCEEEECCCCCEE Q ss_conf 13998683211005998899989998875426789999877421488078608876216778986335113103688617 Q gi|254780451|r 126 VDLVIDHSLIVDYSGNKDAVTRNKDLEYQRNEERYRFLKWGQKSFKNFRVVPPGTGICHQINLEYLGQSVWTKNENGENI 205 (896) Q Consensus 126 ~dlviDHsv~vd~~g~~~a~~~n~~~e~~rN~Ery~Flkwa~~~f~~~~v~pPG~GI~HQvnlE~la~vv~~~~~~~~~~ 205 (896) T Consensus 87 a~iHCDH-LI~~~~G~~kDL~~~~~----~N~EVfDFL~s~~~kY-gi~FW~PGsGIIHQivLE--------------Ny 146 (761) T TIGR01340 87 ASIHCDH-LIVGQKGGEKDLARAIA----TNKEVFDFLESAAKKY-GIGFWKPGSGIIHQIVLE--------------NY 146 (761) T ss_pred CCCCCCC-EEECCCCCCHHHHHHHH----HHHHHHHHHHHHHHHC-CCCCCCCCCCEEEHHHHH--------------HC T ss_conf 5012451-05547786034788886----4015778899766541-886468888404132123--------------10 Q ss_pred EEEE-EEEECCCCCCCCCCCHHHHCCCCHHHHHHHHCCCCCEECCCCEEEEEEECCCCCCCCHHHHHHHHHHHHCCCCCC Q ss_conf 9830-132068876444520123203434899999707751411672899999767786443688999999984102212 Q gi|254780451|r 206 AYPD-TCVGTDSHTTMINALGILGWGVGGIEAEAAMLGCPISMLLPEVVGFEVTGSLQEGVTATDLVLTITQMLRKEGVV 284 (896) Q Consensus 206 a~Pd-tlVGtDSHT~~~galG~la~GVGg~eaea~mlGqp~~~~vPevigv~L~G~L~~gVtakDiiL~i~~~Lr~~Gvv 284 (896) T Consensus 147 a~PGllMlGTDSHtPNaGGL~~~~IGVGGADAVd~l~g~PWELKaPKilGV~LTGkl~gW~~pKDvIlklag~LTV~GGT 226 (761) T TIGR01340 147 AFPGLLMLGTDSHTPNAGGLGAIAIGVGGADAVDALAGLPWELKAPKILGVKLTGKLNGWTSPKDVILKLAGLLTVRGGT 226 (761) T ss_pred CCCCCCCCCCCCCCCCCHHHHHHEECCCCHHHHHHHCCCCHHHCCCCEEEEEEEEEECCCCCHHHHHHHHCCCEEECCCC T ss_conf 24641000456788862213312002673558899718873143880565554101368776224552120411510785 Q ss_pred CEEEEEEECCCCCCCHHHHHHHHCCCCCCCCCEEEECCCHHHHHHHHHCCCCH--HHHHHHHHHHHHHHC--CCCCCCCC Q ss_conf 12799961550017875632120001003720377519989999998639998--899999987464102--36767667 Q gi|254780451|r 285 SKFVEFFGSGFESMVLADRATIANMAPEYGATCGFFPVDRGTIDYLRLSGRSN--SRVDLVEAYTKVQGM--WREDIDYE 360 (896) Q Consensus 285 gk~vEf~G~gi~~LS~~dRaTIaNMa~E~GAt~gifp~De~T~~YL~~tGR~~--~~v~lve~Y~ka~~l--~~~~~~d~ 360 (896) T Consensus 227 G~IvEYfG~Gv~slSCtGm~TiCNMGAEIGATTS~FPf~~~~~~YLkaT~R~~~~~~A~nfenftkG~~~~~~~~~~aD~ 306 (761) T TIGR01340 227 GYIVEYFGPGVESLSCTGMATICNMGAEIGATTSLFPFNEAMKRYLKATNRAEIAEEAKNFENFTKGVAKYKFELLKADK 306 (761) T ss_pred CEEEEEECCCCCCEECCCCHHHHHCCCCCCCCCCCCCHHHHHHHHHHCCCHHHHHHHHHHHHHHHHHHHHHHHHHHHHCC T ss_conf 40898855884741226621232144302000367865578899862217557889988766664223467899875046 Q ss_pred CCCCCEEEEEECCCCCCHHCCCCCCCCEEEHHHHHHHHHHHHHHHCCCHHHHHHHCCCCCCCCCCCCCCEEEEEEECCCC Q ss_conf 88630699998031430122656656413677730116687664001100232102457888887555445753104676 Q gi|254780451|r 361 KVAFTKKMKLDLGNVSPSVAGPRRPESRLSLSEVPSSFVTEMNEYYKKSHTLDEKYPVKGCDFHLKHGDVAIASITSCTN 440 (896) Q Consensus 361 ~a~Y~~vieiDLs~ieP~VAgP~~P~d~v~l~~v~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~l~~g~VvIAaIgSCTN 440 (896) T Consensus 307 ~a~YD~lIEI~Ls~lEPHvNGPFTPDLs~PiS~~~e~~~-------------~~~wP~----------~~~~GLIGSCTN 363 (761) T TIGR01340 307 GAEYDELIEIDLSKLEPHVNGPFTPDLSTPISKFKEKVK-------------KNGWPE----------KLSAGLIGSCTN 363 (761) T ss_pred CCCCCEEEEEECCCCCCCCCCCCCCCCCCHHHHHHHHHH-------------HHCCCC----------EEEEEEEECCCC T ss_conf 888652675111227887687887221432678876565-------------517952----------254423541356 Q ss_pred CCCHHHHHHHHHHHHHHHHCCCCCCCCCEEEEECCCHHHHHHHHHCCCHHHHHHHCCEECCCCCCCCCCCCCCCCCHHHH Q ss_conf 54599987788999889864987586730797016189999999858857777505302055322421277768830221 Q gi|254780451|r 441 TFNPSVMIGAGLLARNAVRAGLKSKPWVKTSCAPGSQVSYEYLVQAGLVEYLEALGFSLVGFGCTTCIGNSGALKKEISE 520 (896) Q Consensus 441 tSnp~~miaAgllAkkAv~~Glkv~p~Vkt~l~PGS~~V~~~L~~~Gll~~L~~aGf~i~~~GCg~CiGnsG~l~~~i~~ 520 (896) T Consensus 364 SS-YeDM~R~~si~k~A~~~G~K~~--~~F~vTPGSEqIRATlERDg~~~~f~~~Gg~vLaNACGPCIGQ---W~R~D~- 436 (761) T TIGR01340 364 SS-YEDMSRCASIVKDAEKAGLKPK--IPFFVTPGSEQIRATLERDGILQTFEKFGGVVLANACGPCIGQ---WDRKDV- 436 (761) T ss_pred CC-HHHHHHHHHHHHHHHHCCCCCC--CCCEECCCCCCCEEEEEECCHHHHHHHCCCEEEECCCCCCCCC---CCCCCC- T ss_conf 66-3145789999999994889755--6732468862100011117668998646878973466888776---553146- Q ss_pred HCCCCCEEEEEEECCCCCCCCCC--CCCCCCEEECCHHHHHHHHHHCCCCCCCCCCCCCCCCCCCCCCCCCCCCCHHHHH Q ss_conf 01136635878633676666546--8543310005978999998516122231002355488886320015688857888 Q gi|254780451|r 521 VIHQKSLVVAGVLSGNRNFEGRI--SPDVEANYLLSPPLVVAYALAGNVRKNLIKDPIGEDQQGSPVYLRDIWPKDSEIQ 598 (896) Q Consensus 521 ~i~~~~l~~~sV~SgNRNFeGR~--~p~~~~~yLaSP~lVvA~AiaG~I~~d~~~dplg~~~~G~~v~L~DiwPs~~Ei~ 598 (896) T Consensus 437 s~~kg~~N-~I~tSyNRNF~gRND~N~~T-~~Fl~SPelVtAm~~aG~~~FNPlTD~~-~~~dGK~FKl~a--P~GdelP 511 (761) T TIGR01340 437 SVKKGEPN-TILTSYNRNFRGRNDGNPAT-MNFLASPELVTAMSYAGSLKFNPLTDSL-KTPDGKEFKLKA--PKGDELP 511 (761) T ss_pred CCCCCCCC-CEEEECCCCCCCCCCCCHHH-HCCCCCHHHHHHHHHHCCCCCCCCCCCC-CCCCCCCCCCCC--CCCCCCC T ss_conf 32578975-14740366766647467323-1001567898898760657457653200-188885004683--5788878 Q ss_pred HHHHHHCCCCCCCCCCCCCCCCCHHHCCCCCCCCCCCCCCCCCCCCCC-CCCCCCCCCCCCCCCCCCCCEEEEEECCCCC Q ss_conf 887641583210001223347871220155787762056743334237-8876776545543324358558999658857 Q gi|254780451|r 599 SFVNKYVTCDLYKKKYSDVFKGDSSWWNIEVPESETYMWDEKSTYVRN-PPYFETISKHIPEIVDICGARILCLLGDKIT 677 (896) Q Consensus 599 ~~~~~~v~~~~f~~~y~~i~~g~~~w~~l~~~~~~~y~w~~~StyI~~-pPff~~~~~~~~~~~~i~~arvL~~lGD~iT 677 (896) T Consensus 512 ~~G-----F~~Gr~~f~~~~~-~kP~~nv~v------av~P~S~RLqLLePF------~~w~g~dl~g~~vL~Kv~GKcT 573 (761) T TIGR01340 512 EKG-----FEAGRDTFQAPPD-SKPDENVEV------AVDPKSDRLQLLEPF------EPWNGKDLKGLRVLIKVEGKCT 573 (761) T ss_pred CCC-----CCCCCCCEECCCC-CCCCCCCEE------EECCCCCHHHHCCCC------CCCCCCCCCCCEEEEEECCCCC T ss_conf 887-----6246651315867-888885337------867885278651777------7788863237757898414237 Q ss_pred HHHCCCCCCCCCCCCHHHHHHHCCCCHHHHHHHHHHCCCHHHHHHHHHCCCHHHHHHCCCCCCCCCCE---EECCCCCEE Q ss_conf 23316456555447378889874988656314565302357776652036012232125777657722---453899787 Q gi|254780451|r 678 TDHISPAGSIPLQSAAASYLRQRGVKEKDFNQFGTRRGNHEVMMRGTFSNIRICNYMLGEEGKKGGYT---IHYPSKEEL 754 (896) Q Consensus 678 TDHISPAG~I~~~spAg~yL~~~Gv~~~dfNsygsRRgNhevM~RGtFaNirl~N~l~~~~~~egg~T---~~~p~~~~~ 754 (896) T Consensus 574 TDhISaAG---------pWLKYkGHL~NIS~-----------------------N~LigA~N~e~gE~N~~~~~~~G~~~ 621 (761) T TIGR01340 574 TDHISAAG---------PWLKYKGHLDNISN-----------------------NTLIGAVNAETGEVNKAYDLFDGSKG 621 (761) T ss_pred CCCCCCCC---------CCCCCCCCCHHHHH-----------------------HHHHHHCCHHCCCCHHHHHCCCCCCC T ss_conf 46301367---------62123678312222-----------------------33543013000640101102688634 Q ss_pred EHHHHHHHHHHCCCCEEEECCCCCCCCCHHHHHHHHHHHCCEEEEEECCHHHHHHHCCCCCEEEEEECCCCCCHHHHCCC Q ss_conf 37999998998199889994677786730799988667617089997647898885053552322331789898881989 Q gi|254780451|r 755 FIYDAAMRYKVDQVPLVVFAGVEYGNGSSRDWAAKGTRLLGVRSVIAESFERIHRSNLIGMGVIPFAFGKGISWKNLNIK 834 (896) Q Consensus 755 ~iydaA~~Y~~~~~plVViAG~~YG~GSSRdwAAkgp~lLGVkAVIA~SFeRIHrsNLv~mGiLPL~F~~~~~~~~L~l~ 834 (896) T Consensus 622 ~iP~~a~~yK~~g~~W~vva~~NYGEGSaREHAAL~PR~LGg~~i~~kSFARIHETNLKKQG~lPLTFAn~~DYDk--I~ 699 (761) T TIGR01340 622 DIPELARDYKARGVKWVVVAEHNYGEGSAREHAALEPRHLGGRIIIVKSFARIHETNLKKQGVLPLTFANEADYDK--IQ 699 (761) T ss_pred CCHHHHHHHHHCCCCEEEEECCCCCCCCHHHHHHCCCCCCCCEEEEEECCCHHHHHCCCCCCCCCCCCCCCCCCCC--CC T ss_conf 6137999997579846998016578765355640586100745777601001221112104766533577233454--48 Q ss_pred CCEEEEEECHHHCCC-----CCEEEEEEEECC-CCEEEEEEEEEECCHHHHHHHHCCCHHHHH Q ss_conf 743899726322589-----973899998189-967999999873899999999909836898 Q gi|254780451|r 835 GDEIINIRKLKTISP-----RQESTLEIHYSD-GTFKCVPIICCIDTLDEINHLKNGGILQAV 891 (896) Q Consensus 835 G~E~~~i~~~~~l~p-----~~~v~v~i~~~~-g~~~~~~~~~r~dt~~E~~~~~~GGiL~yv 891 (896) T Consensus 700 ~~d~~~~lnl~~l~~kd~~~g~~~~~~v~~k~tg~~~~iK~~Ht~-~~~Qi~ffkaGSAlN~~ 761 (761) T TIGR01340 700 PGDEVELLNLVELLKKDNNNGGEVDLRVTKKNTGKVFEIKLKHTL-SKDQIGFFKAGSALNLL 761 (761) T ss_pred CCCEEEEECHHHHHHHCCCCCCEEEEEEECCCCCCEEEEEECCCC-CHHHHHHHHHHHHHCCC T ss_conf 876164200233454118898647899752899956887411255-76678998754664159

HHsearch alignment for GI: 254780451 and conserved domain: TIGR01340