Center for Structural Genomics of Infectious Diseases

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Structure of IDP04634

Description: Citrate synthase is a member of a small family of enzymes that can directly form a carbon-carbon bond without the presence of metal ion cofactors. It catalyses the first reaction in the Krebs' cycle, namely the conversion of oxaloacetate and acetyl-coenzyme A into citrate and coenzyme A. This reaction is important for energy generation and for carbon assimilation. The reaction proceeds via a non-covalently bound citryl-coenzyme A intermediate in a 2-step process (aldol-Claisen condensation followed by the hydrolysis of citryl-CoA). The protein monomer is composed of two domains: a large alpha-helical domain consisting of two structural repeats, where the second repeat is interrupted by a small alpha-helical domain. The cleft between these domains forms the active site, where both citrate and acetyl-coenzyme A bind. The enzyme undergoes a conformational change upon binding of the oxaloacetate ligand, whereby the active site cleft closes over in order to form the acetyl-CoA binding site. Crystal Structure of Citrate Synthase from Francisella tularensis complexed with oxaloacetate ion was solved at 1.85A and represents dimer in the crystal.
Functional assignment

Ligand code	Name	Ligand type
TRS	2-AMINO-2-HYDROXYMETHYL-PROPANE-1,3-DIOL	crystallization
OAA	oxaloacetate ion	biological
ZN	zinc
CL	chloride
SO4	sulfate
ACY