5kbz

Structure of the PksA Product Template domain in complex with a phosphopantetheine mimetic

spinqualitylabelsall models 5kbz, resolution 1.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 5kbz is a 2 chain structure with sequence from Asppa. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: 3B2 Related: 3hrr Gene: pksL1, aflC, pksA (ASPPA) Activity: Noranthrone synthase, with EC number 2.3.1.221 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [PKSL1_ASPPA] Combines a hexanoyl starter unit and 7 malonyl-CoA extender units to synthesize the precursor norsolorinic acid anthrone (noranthrone) in the aflatoxin biosynthesis pathway. The hexanoyl starter unit is provided to the acyl-carrier protein (ACP) domain by a dedicated fungal fatty acid synthase. Publication Abstract from PubMed Product template (PT) domains from fungal nonreducing polyketide synthases (NR-PKSs) are responsible for controlling the aldol cyclizations of poly-beta-ketone intermediates assembled during the catalytic cycle. Our ability to understand the high regioselective control that PT domains exert is hindered by the inaccessibility of intrinsically unstable poly-beta-ketones for in vitro studies. We describe here the crystallographic application of "atom replacement" mimetics in which isoxazole rings linked by thioethers mimic the alternating sites of carbonyls in the poly-beta-ketone intermediates. We report the 1.8-A cocrystal structure of the PksA PT domain from aflatoxin biosynthesis with a heptaketide mimetic tethered to a stably modified 4'-phosphopantetheine, which provides important empirical evidence for a previously proposed mechanism of PT-catalyzed cyclization. Key observations support the proposed deprotonation at C4 of the nascent polyketide by the catalytic His1345 and the role of a protein-coordinated water network to selectively activate the C9 carbonyl for nucleophilic addition. The importance of the 4'-phosphate at the distal end of the pantetheine arm is demonstrated to both facilitate delivery of the heptaketide mimetic deep into the PT active site and anchor one end of this linear array to precisely meter C4 into close proximity to the catalytic His1345. Additional structural features, docking simulations, and mutational experiments characterize protein-substrate mimic interactions, which likely play roles in orienting and stabilizing interactions during the native multistep catalytic cycle. These findings afford a view of a polyketide "atom-replaced" mimetic in a NR-PKS active site that could prove general for other PKS domains. Polyketide mimetics yield structural and mechanistic insights into product template domain function in nonreducing polyketide synthases.,Barajas JF, Shakya G, Moreno G, Rivera H Jr, Jackson DR, Topper CL, Vagstad AL, La Clair JJ, Townsend CA, Burkart MD, Tsai SC Proc Natl Acad Sci U S A. 2017 May 8. pii: 201609001. doi:, 10.1073/pnas.1609001114. PMID:28484029 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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