7vef

The structure of GfsA KSQ-AT didomain in complex with a malonate substrate analog

spinqualitylabelsall models 7vef, resolution 2.65Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 7vef is a 1 chain structure with sequence from Streptomyces graminofaciens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.65Å Ligands: 6IU, GOL Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function E0D202_9ACTN Publication Abstract from PubMed Ketosynthase-like decarboxylase (KSQ) domains are widely distributed in the loading modules of modular polyketide synthases (PKSs) and are proposed to catalyze the decarboxylation of a malonyl or methylmalonyl unit for the construction of the PKS starter unit. KSQ domains have high sequence similarity to ketosynthase (KS) domains, which catalyze transacylation and decarboxylative condensation in polyketide and fatty acid biosynthesis, except that the catalytic Cys residue of KS domains is replaced by Gln in KSQ domains. Here, we present biochemical analyses of GfsA KSQ and CmiP4 KSQ, which are involved in the biosynthesis of FD-891 and cremimycin, respectively. In vitro analysis showed that these KSQ domains catalyze the decarboxylation of malonyl and methylmalonyl units. Furthermore, we determined the crystal structure of GfsA KSQ in complex with a malonyl thioester substrate analogue, which enabled identification of key amino acid residues involved in the decarboxylation reaction. The importance of these residues was confirmed by mutational analysis. On the basis of these findings, we propose a mechanism of the decarboxylation reaction catalyzed by GfsA KSQ. GfsA KSQ initiates decarboxylation by fixing the substrate in a suitable conformation for decarboxylation. The formation of enolate upon decarboxylation is assisted by two conserved threonine residues. Comparison of the structure of GfsA KSQ with those of KS domains suggests that the Gln residue in the active site of the KSQ domain mimics the acylated Cys residue in the active site of KS domains. Structural Insight into the Reaction Mechanism of Ketosynthase-Like Decarboxylase in a Loading Module of Modular Polyketide Synthases.,Chisuga T, Nagai A, Miyanaga A, Goto E, Kishikawa K, Kudo F, Eguchi T ACS Chem Biol. 2022 Jan 5. doi: 10.1021/acschembio.1c00856. PMID:34985877 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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