4EIA: Activator Of The 2-Hydroxyisocaproyl-Coa Dehydratase From Clostridium Difficile Without Nucleotide

Members of the 2-hydroxyacyl-CoA dehydratase enzyme family catalyze the beta,alpha-dehydration of various CoA-esters in the fermentation of amino acids by clostridia. Abstraction of the nonacidic beta-proton of the 2-hydroxyacyl-CoA compounds is achieved by the reductive generation of ketyl radicals on the substrate, which is initiated by the transfer of an electron at low redox potentials. The highly energetic electron needed on the dehydratase is donated by a [4Fe-4S] cluster containing ATPase, termed activator. We investigated the activator of the 2-hydroxyisocaproyl-CoA dehydratase from Clostridium difficile. The activator is a homodimeric protein structurally related to acetate and sugar kinases, Hsc70 and actin, and has a [4Fe-4S] cluster bound in the dimer interface. The crystal structures of the Mg-ADP, Mg-ADPNP, and nucleotide-free states of the reduced activator have been solved at 1.6-3.0 A resolution, allowing us to define the position of Mg(2+) and water molecules in the vicinity of the nucleotides and the [4Fe-4S] cluster. The structures reveal redox- and nucleotide dependent changes agreeing with the modulation of the reduction potential of the [4Fe-4S] cluster by conformational changes. We also investigated the propensity of the activator to form a complex with its cognate dehydratase in the presence of Mg-ADP and Mg-ADPNP and together with the structural data present a refined mechanistic scheme for the ATP-dependent electron transfer between activator and dehydratase.
PDB ID: 4EIADownload
MMDB ID: 101869
PDB Deposition Date: 2012/4/5
Updated in MMDB: 2012/09
Experimental Method:
x-ray diffraction
Resolution: 3  Å
Source Organism:
Similar Structures:
Biological Unit for 4EIA: dimeric; determined by author and by software (PISA)
Molecular Components in 4EIA
Label Count Molecule
Proteins (2 molecules)
Activator of 2-hydroxyisocaproyl-coa Dehydratase
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

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