|Iron-sulphur cluster||Formal oxidation/spin states|
Aconitase (aconitate hydratase; EC 126.96.36.199) catalyses the stereospecific isomerisation of citrate to isocitrate via cisaconitate in the tricarboxylic acid cycle, a nonredox active process .
The ironresponsive element binding protein (IREBP) and 3isopropylmalate dehydratase (isopropylmalate isomerase; EC 188.8.131.52), an enzyme catalysing the second step in the biosynthesis of leucine, are known aconitase homologues . Iron regulatory elements (IREs) constitute a family of 28nucleotide, noncoding, stemloop structures that regulate iron storage, haem synthesis and iron uptake. They also participate in ribosome binding and control the mRNA turnover (degradation). The specific regulator protein, the IREBP, binds to IREs in both 5' and 3' regions , but only to RNA in the apo form, without the Fe-S cluster. Expression of IREBP in cultured cells has revealed that the protein functions either as an active aconitase, when cells are ironreplete, or as an active RNAbinding protein, when cells are irondepleted . Mutant IREBPs, in which any or all of the three cysteine residues involved in Fe-S formation are replaced by serines, have no aconitase activity, but retain RNAbinding properties .
The 3D structure of mitochondrial aconitase has been determined
, and has been shown to contain four
/ß domains: the three
Nterminal domains have similar folds, each with three
ß layers, while the Cterminal domain forms a
ßbarrel (see Figure 7ACN).
Aconitase family proteins in enzyme databases
|ENZYME||LIGAND||BRENDA||Official name||Alternative name(s)|
|Aconitate hydratase||Aconitase; citrate hydrolyase|
|3Isopropylmalate dehydratase||Isopropylmalate isomerase|
|PRINTS ID||PRINTS AC||PROSITE/BLOCKS ID||PROSITE AC||BLOCKS AC|
|Protein Superfamily||Pfam||LPFC 3D alignment|
|80062; (aconitate hydratase / IREBP)|
|1aco||1aco||1aco||1aco||Aconitase (complex with transaconitate); bovine heart|
|1ami||1ami||1ami||1ami||Aconitase (complex with methylisocitrate); bovine heart|
|1amj||1amj||1amj||1amj||Aconitase (complex with sulphate and hydroxide); bovine heart|
|1b0j||1ar3||1b0j||Aconitase (S642A mutant) (complex with isocitrate); pig heart|
|1b0k||1as9||1b0k||Aconitase (S642A mutant) (complex with fluorocitrate); pig heart|
|1b0m||1atq||1b0m||Aconitase (R644Q mutant) (complex with fluorocitrate); pig heart|
|1fgh||1fgh||1fgh||1fgh||Aconitase (complex with 4hydroxytransaconitate); bovine heart|
|1nis||1nis||1nis||1nis||Aconitase (complex with nitrocitrate) (major occupancy form); bovine heart|
|1nit||1nit||1nit||1nit||Aconitase (complex with sulphate) (minor occupancy form); bovine heart|
|5acn*||5acn*||5acn*||5acn*||Aconitase (inactive [Fe3S4] cluster form) (complex with sulphate and tricarballylic acid); pig heart|
|6acn||6acn||6acn||6acn||Aconitase (activated [Fe4S4] cluster form) (complex with sulphate and tricarballylic acid); pig heart|
|7acn||7acn||7acn||7acn||Aconitase (complex with isocitrate); pig heart||MMS93002|
|8acn||8acn||8acn||8acn||Aconitase (complex with nitroisocitrate); bovine heart||MMS93002|
¹ Macromolecular Structures abstract.
Full text is available to BioMedNet
|Bibliography on structural studies of aconitase|
|Reviews on aconitase|