8cg5

The ACP crosslinked to the KS of the cercosporin fungal non-reducing polyketide synthase (NR-PKS) CTB1 (SAT-KS:ACP-MAT)

spinqualitylabelsall models 8cg5, resolution 2.70Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 8cg5 is a 3 chain structure with sequence from Cercospora nicotianae. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 2.7Å Ligands: 42X Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function CTB1_CERNC Polyketide synthase; part of the gene cluster that mediates the biosynthesis of cercosporin, a light-activated, non-host-selective toxin (PubMed:12937958, PubMed:15915645, PubMed:26938470, PubMed:29610486). The perylenequinone chromophore of cercosporin absorbs light energy to attain an electronically-activated triplet state and produces active oxygen species such as the hydroxyl radical, superoxide, hydrogen peroxide or singlet oxygen upon reaction with oxygen molecules (PubMed:11701851). These reactive oxygen species cause damage to various cellular components including lipids, proteins and nucleic acids (PubMed:11701851). The first step of cercosporin biosynthesis is performed by the polyketide synthase CTB1 which catalyzes the formation of nor-toralactone (PubMed:23108075, PubMed:26938470, PubMed:29610486). The starter unit acyltransferase (SAT) domain of CTB1 initiates polyketide extension by the selective utilization of acetyl-CoA, which is elongated to the heptaketide in the beta-ketoacyl synthase (KS) domain by successive condensations with six malonyl units introduced by the malonyl acyltransferase (MAT) domain. The product template (PT) domain catalyzes C4-C9 and C2-C11 aldol cyclizations and dehydrations to a trihydroxynaphthalene, which is thought to be delivered to the thioesterase (TE) domain for product release (PubMed:23108075, PubMed:29610486). The bifunctional enzyme CTB3 then methylates nor-toralactone to toralactone before conducting an unusual oxidative aromatic ring opening (PubMed:17074519, PubMed:26938470). The O-methyltransferase CTB2 further methylates the nascent OH-6 of the CBT3 product, blocking further oxidation at this site before the reductase CTB6 reduces the 2-oxopropyl ketone at position C7, giving naphthalene (PubMed:17660442, PubMed:26938470). The FAD-dependent monooxygenase CTB5 in concert with the multicopper oxidase CTB12 are responsible for homodimerization of naphthalene with CTB7 installing the dioxepine moiety, finally producing cercosporin (PubMed:17660442, PubMed:26938470, PubMed:30809363). The fasciclin domain-containing protein CTB11 might act with CTB5 and CTB12 whereas the roles of CTB9 and CTB10 have still to be elucidated (By similarity).[UniProtKB:Q0UHZ9]

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