ジャーナル: Nat Chem Biol / 年: 2018 タイトル: The structural organization of substrate loading in iterative polyketide synthases. 著者: Dominik A Herbst / Callie R Huitt-Roehl / Roman P Jakob / Jacob M Kravetz / Philip A Storm / Jamie R Alley / Craig A Townsend / Timm Maier / 要旨: Polyketide synthases (PKSs) are microbial multienzymes for the biosynthesis of biologically potent secondary metabolites. Polyketide production is initiated by the loading of a starter unit onto an ...Polyketide synthases (PKSs) are microbial multienzymes for the biosynthesis of biologically potent secondary metabolites. Polyketide production is initiated by the loading of a starter unit onto an integral acyl carrier protein (ACP) and its subsequent transfer to the ketosynthase (KS). Initial substrate loading is achieved either by multidomain loading modules or by the integration of designated loading domains, such as starter unit acyltransferases (SAT), whose structural integration into PKS remains unresolved. A crystal structure of the loading/condensing region of the nonreducing PKS CTB1 demonstrates the ordered insertion of a pseudodimeric SAT into the condensing region, which is aided by the SAT-KS linker. Cryo-electron microscopy of the post-loading state trapped by mechanism-based crosslinking of ACP to KS reveals asymmetry across the CTB1 loading/-condensing region, in accord with preferential 1:2 binding stoichiometry. These results are critical for re-engineering the loading step in polyketide biosynthesis and support functional relevance of asymmetric conformations of PKSs.
解像度: 2.77→63.45 Å / SU ML: 0.46 / 交差検証法: FREE R-VALUE / σ(F): 1.34 / 位相誤差: 27.1 / 立体化学のターゲット値: ML 詳細: UNIDENTIFIED DIFFERENCE DENSITY AROUND THE ACTIVE SITE RESIDUES C553 AND C119, POSSIBLY DUE TO PARTIAL ACYLATION OR OXIDATION. THE DIFFERENCE DENSITY IN THE REGION AROUND RESIDUES 651 TO 661 ...詳細: UNIDENTIFIED DIFFERENCE DENSITY AROUND THE ACTIVE SITE RESIDUES C553 AND C119, POSSIBLY DUE TO PARTIAL ACYLATION OR OXIDATION. THE DIFFERENCE DENSITY IN THE REGION AROUND RESIDUES 651 TO 661 INDICATES MULTIPLE DIFFERENT MAIN CHAIN CONFORMATION, WHEREAS ONLY ONE COULD ME MODELLED. BASED ON OBSERVED B-FACTORS AND THE FACT THAT CRYSTALLIZATION WAS CARRIED OUT IN THE PRESENCE OF 0.3M MG(2+) SOME SURFACE WATERS MIGHT ALSO REPRESENT PARTIALLY OCCUPIED HYDRATED MAGNESIUM IONS.
Rfactor
反射数
%反射
Rfree
0.2405
3916
4.91 %
Rwork
0.2052
-
-
obs
0.2069
79812
99.04 %
溶媒の処理
減衰半径: 0.9 Å / VDWプローブ半径: 1.11 Å / 溶媒モデル: FLAT BULK SOLVENT MODEL