2Q34

Crystal Structure of the ECH2 decarboxylase domain of CurF from Lyngbya majuscula, rhombohedral crystal form

Summary for 2Q34

• Entry DOI: 10.2210/pdb2q34/pdb
• Related: 2Q2X 2Q35
• Descriptor: CurF (2 entities in total)
• Functional Keywords: crotonase, lyase
• Biological source: Lyngbya majuscula
• Total number of polymer chains: 1
• Total formula weight: 27099.37

Authors

Geders, T.W.,Mowers, J.C.,Smith, J.L. (deposition date: 2007-05-29, release date: 2007-10-09, Last modification date: 2023-11-15)

Primary citation

Geders, T.W.,Gu, L.,Mowers, J.C.,Liu, H.,Gerwick, W.H.,Hakansson, K.,Sherman, D.H.,Smith, J.L.
Crystal structure of the ECH2 catalytic domain of CurF from Lyngbya majuscula. Insights into a decarboxylase involved in polyketide chain beta-branching.
J.Biol.Chem., 282:35954-35963, 2007

PubMed Abstract: Curacin A is a mixed polyketide/nonribosomal peptide possessing anti-mitotic and anti-proliferative activity. In the biosynthesis of curacin A, the N-terminal domain of the CurF multifunctional protein catalyzes decarboxylation of 3-methylglutaconyl-acyl carrier protein (ACP) to 3-methylcrotonyl-ACP, the postulated precursor of the cyclopropane ring of curacin A. This decarboxylase is encoded within an "HCS cassette" that is used by several other polyketide biosynthetic systems to generate chemical diversity by introduction of a beta-branch functional group to the natural product. The crystal structure of the CurF N-terminal ECH(2) domain establishes that the protein is a crotonase superfamily member. Ala(78) and Gly(118) form an oxyanion hole in the active site that includes only three polar side chains as potential catalytic residues. Site-directed mutagenesis and a biochemical assay established critical functions for His(240) and Lys(86), whereas Tyr(82) was nonessential. A decarboxylation mechanism is proposed in which His(240) serves to stabilize the substrate carboxylate and Lys(86) donates a proton to C-4 of the acyl-ACP enolate intermediate to form the Delta(2) unsaturated isopentenoyl-ACP product. The CurF ECH(2) domain showed a 20-fold selectivity for ACP-over CoA-linked substrates. Specificity for ACP-linked substrates has not been reported for any other crotonase superfamily decarboxylase. Tyr(73) may select against CoA-linked substrates by blocking a contact of Arg(38) with the CoA adenosine 5'-phosphate.

PubMed: 17928301
DOI: 10.1074/jbc.M703921200

Experimental method

X-RAY DIFFRACTION (1.85 Å)