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Crystal structures of aconitase with trans-aconitate and nitrocitrate bound.
J Mol Biol. 1994 Apr 08; 237(4):437-51.JM

Abstract

Crystal structures of mitochondrial aconitase with the inhibitors trans-aconitate and nitrocitrate bound to the [4Fe-4S] cluster have been solved and refined at 2.05 A resolution with R-factors of 0.168 and 0.172, respectively. Crystallization of aconitase with the substrates citrate and cis-aconitate has not been possible because the enzyme turns over and selects enzyme with isocitrate bound into the crystal lattice. Therefore we have analyzed crystal structures of the enzyme complexed with inhibitor analogs of these two substrates. The structure with nitrocitrate bound provides a model for citrate binding. The structure with trans-aconitate bound provides a model for cis-aconitate binding in two ways: Fe4 of the [4Fe-4S] cluster is five-coordinate and the carbon at the C beta position is trigonal. These results allow the model for the reaction mechanism to be extended to all three natural substrates of aconitase. The results support a model in which citrate and isocitrate form similar chelate structures related by 180 degrees rotation about the C alpha-C beta bond while the intermediate cis-aconitate binds in either of two ways (citrate mode or isocitrate mode). In both inhibitor complexes a H2O molecule is also bound to Fe4. In the structure with nitrocitrate bound, partial occupancy of sulfate in the active site is observed accompanied by hydroxyl binding to Fe4. Comparison of the structures with isocitrate, trans-aconitate, nitrocitrate and sulfate bound reveals preferred orientations for the three types of oxygens ligated to Fe4 (carboxyl, hydroxyl and H2O) supporting the proposed roles for His101, Asp165 and His167 in the catalytic mechanism.

Authors+Show Affiliations

Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

8151704

Citation

Lauble, H, et al. "Crystal Structures of Aconitase With Trans-aconitate and Nitrocitrate Bound." Journal of Molecular Biology, vol. 237, no. 4, 1994, pp. 437-51.
Lauble H, Kennedy MC, Beinert H, et al. Crystal structures of aconitase with trans-aconitate and nitrocitrate bound. J Mol Biol. 1994;237(4):437-51.
Lauble, H., Kennedy, M. C., Beinert, H., & Stout, C. D. (1994). Crystal structures of aconitase with trans-aconitate and nitrocitrate bound. Journal of Molecular Biology, 237(4), 437-51.
Lauble H, et al. Crystal Structures of Aconitase With Trans-aconitate and Nitrocitrate Bound. J Mol Biol. 1994 Apr 8;237(4):437-51. PubMed PMID: 8151704.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Crystal structures of aconitase with trans-aconitate and nitrocitrate bound. AU - Lauble,H, AU - Kennedy,M C, AU - Beinert,H, AU - Stout,C D, PY - 1994/4/8/pubmed PY - 1994/4/8/medline PY - 1994/4/8/entrez SP - 437 EP - 51 JF - Journal of molecular biology JO - J Mol Biol VL - 237 IS - 4 N2 - Crystal structures of mitochondrial aconitase with the inhibitors trans-aconitate and nitrocitrate bound to the [4Fe-4S] cluster have been solved and refined at 2.05 A resolution with R-factors of 0.168 and 0.172, respectively. Crystallization of aconitase with the substrates citrate and cis-aconitate has not been possible because the enzyme turns over and selects enzyme with isocitrate bound into the crystal lattice. Therefore we have analyzed crystal structures of the enzyme complexed with inhibitor analogs of these two substrates. The structure with nitrocitrate bound provides a model for citrate binding. The structure with trans-aconitate bound provides a model for cis-aconitate binding in two ways: Fe4 of the [4Fe-4S] cluster is five-coordinate and the carbon at the C beta position is trigonal. These results allow the model for the reaction mechanism to be extended to all three natural substrates of aconitase. The results support a model in which citrate and isocitrate form similar chelate structures related by 180 degrees rotation about the C alpha-C beta bond while the intermediate cis-aconitate binds in either of two ways (citrate mode or isocitrate mode). In both inhibitor complexes a H2O molecule is also bound to Fe4. In the structure with nitrocitrate bound, partial occupancy of sulfate in the active site is observed accompanied by hydroxyl binding to Fe4. Comparison of the structures with isocitrate, trans-aconitate, nitrocitrate and sulfate bound reveals preferred orientations for the three types of oxygens ligated to Fe4 (carboxyl, hydroxyl and H2O) supporting the proposed roles for His101, Asp165 and His167 in the catalytic mechanism. SN - 0022-2836 UR - https://www.unboundmedicine.com/medline/citation/8151704/Crystal_structures_of_aconitase_with_trans_aconitate_and_nitrocitrate_bound_ DB - PRIME DP - Unbound Medicine ER -