Aconitase

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'''Aconitase (ACO)''' is an enzymatic domain that confers the ability to catalyse the equilibrium
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:citrate = aconitate + H<sub>2</sub>O = isocitrate
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This reaction is part of the citrate (TCA-, Krebs-cycle).
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In most organims, there is a cytosolic enzyme with an ACO domain (cAc), and in metazoa and up, a second copy was forked in mitochondria (mAc). A specialty of cAc is that in mammals it has developed a second function as inhibitor of those mRNA that carry an iron-regulatory element (IRE). Therefore, the cytosolic cAc is named IREBP for IRE-binding protein when this function is talked about. Only one of the two functions is active, depending on whether the (4Fe4S) cofactor is present in the molecule: it's essential for the ACO function.
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== Available structures ==
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In the PDB, nearly all deposited structures are from mammals, [[1l5j]] is from ''E.coli''. Also, only [[2ipy]] shows the IREBP function of cAc---it's also the only from rabbit. There are only two other cAc structures, with and without citrate, also the only from human. All other structures are either cow or pig, and a mutant from pig; all three proteins with several different ligands and inhibitors.
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*[[1aco]] - mAc (''Bos taurus'') with ''trans''-aconitate (inhibitor)
*[[1aco]] - mAc (''Bos taurus'') with ''trans''-aconitate (inhibitor)
*[[1ami]] - mAc (''Bos taurus'') with methylisocitrate
*[[1ami]] - mAc (''Bos taurus'') with methylisocitrate

Revision as of 18:40, 16 February 2009

Aconitase (ACO) is an enzymatic domain that confers the ability to catalyse the equilibrium

citrate = aconitate + H2O = isocitrate

This reaction is part of the citrate (TCA-, Krebs-cycle).

In most organims, there is a cytosolic enzyme with an ACO domain (cAc), and in metazoa and up, a second copy was forked in mitochondria (mAc). A specialty of cAc is that in mammals it has developed a second function as inhibitor of those mRNA that carry an iron-regulatory element (IRE). Therefore, the cytosolic cAc is named IREBP for IRE-binding protein when this function is talked about. Only one of the two functions is active, depending on whether the (4Fe4S) cofactor is present in the molecule: it's essential for the ACO function.

Available structures

In the PDB, nearly all deposited structures are from mammals, 1l5j is from E.coli. Also, only 2ipy shows the IREBP function of cAc---it's also the only from rabbit. There are only two other cAc structures, with and without citrate, also the only from human. All other structures are either cow or pig, and a mutant from pig; all three proteins with several different ligands and inhibitors.

  • 1aco - mAc (Bos taurus) with trans-aconitate (inhibitor)
  • 1ami - mAc (Bos taurus) with methylisocitrate
  • 1amj - mAc (Bos taurus) with sulfate and hydroxide
  • 1b0j - S642 mutant of mAc (Sus scrofa) with isocitrate (substrate)
  • 1b0k - S642 mutant of mAc (Sus scrofa) with fluorocitrate (inhibitor)
  • 1b0m - S642 mutant of mAc (Sus scrofa) with fluorocitrate (inhibitor) and oxygen
  • 1c96 - S642 mutant of mAc (Sus scrofa) with citrate
  • 1c97 - S642 mutant of mAc (Sus scrofa) with isocitrate and oxygen
  • 1fgh - mAc (Bos taurus) with 4-hydroxy-trans-aconitate (inhibitor)
  • 1l5j - aconitase B (E. coli) with Fe3S4 and aconitate
  • 1nis - mAc (Bos taurus) with nitrocitrate (inhibitor)
  • 1nit - mAc (Bos taurus) with sulfate
  • 2b3x - cAc (human) as aconitase with Fe4S4
  • 2b3y - cAc (human) as aconitase with Fe4S4 and citrate
  • 2ipy - cAc (Oryctolagus cuniculus) as IRP1 with ferritin RNA
  • 5acn - mAc (Sus scrofa) with Fe3S4 (missing a Fe)
  • 6acn - mAc (Sus scrofa) with Fe4S4
  • 7acn - mAc (Sus scrofa) with isocitrate
  • 8acn - mAc (Sus scrofa) with nitroisocitrate
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