Structural Insights into the Free-Standing Condensation Enzyme SgcC5 Catalyzing Ester-Bond Formation in the Biosynthesis of the Enediyne Antitumor Antibiotic C-1027,Biochemistry

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Structural Insights into the Free-Standing Condensation Enzyme SgcC5 Catalyzing Ester-Bond Formation in the Biosynthesis of the Enediyne Antitumor Antibiotic C-1027
Biochemistry ( IF 2.9 ) Pub Date : 2018-03-13 00:00:00 , DOI: 10.1021/acs.biochem.8b00174
Chin-Yuan Chang ₁ , Jeremy R. Lohman ₁ , Tingting Huang ₁ , Karolina Michalska ₂ , Lance Bigelow ₂ , Jeffrey D. Rudolf ₁ , Robert Jedrzejczak ₂ , Xiaohui Yan ₁ , Ming Ma ₁ , Gyorgy Babnigg _{2,

3} , Andrzej Joachimiak _{2,

3,

4} , George N. Phillips ₅ , Ben Shen _{1,

6,

7}

Affiliation

C-1027 is a chromoprotein enediyne antitumor antibiotic, consisting of the CagA apoprotein and the C-1027 chromophore. The C-1027 chromophore features a nine-membered enediyne core appended with three peripheral moieties, including an (S)-3-chloro-5-hydroxy-β-tyrosine. In a convergent biosynthesis of the C-1027 chromophore, the (S)-3-chloro-5-hydroxy-β-tyrosine moiety is appended to the enediyne core by the free-standing condensation enzyme SgcC5. Unlike canonical condensation domains from the modular nonribosomal peptide synthetases that catalyze amide-bond formation, SgcC5 catalyzes ester-bond formation, as demonstrated in vitro, between SgcC2-tethered (S)-3-chloro-5-hydroxy-β-tyrosine and (R)-1-phenyl-1,2-ethanediol, a mimic of the enediyne core as an acceptor substrate. Here, we report that (i) genes encoding SgcC5 homologues are widespread among both experimentally confirmed and bioinformatically predicted enediyne biosynthetic gene clusters, forming a new clade of condensation enzymes, (ii) SgcC5 shares a similar overall structure with the canonical condensation domains but forms a homodimer in solution, the active site of which is located in a cavity rather than a tunnel typically seen in condensation domains, and (iii) the catalytic histidine of SgcC5 activates the 2-hydroxyl group, while a hydrogen-bond network in SgcC5 prefers the R-enantiomer of the acceptor substrate, accounting for the regio- and stereospecific ester-bond formation between SgcC2-tethered (S)-3-chloro-5-hydroxy-β-tyrosine and (R)-1-phenyl-1,2-ethanediol upon acid–base catalysis. These findings expand the catalytic repertoire and reveal new insights into the structure and mechanism of condensation enzymes.

中文翻译：

对Enediyne Antitumor抗生素C-1027生物合成中的酯键形成催化的酯键缩合酶SgcC5的结构分析。

C-1027是一种色蛋白烯二炔抗肿瘤抗生素，由CagA载脂蛋白和C-1027生色团组成。C-1027发色团的特征是九元烯二炔核心，并附加了三个外围部分，包括（S）-3-氯-5-羟基-β-酪氨酸。在C-1027发色团的聚合生物合成中，（S）-3-氯-5-羟基-β-酪氨酸部分通过独立的缩合酶SgcC5附加到烯二炔核上。与体外催化核糖键形成的模块化非核糖体肽合成酶的规范缩合域不同，SgcC5催化SgcC2连接的（S）-3-氯-5-羟基-β-酪氨酸和（[R）-1-苯基-1,2-乙二醇，是二烯炔核心的模拟物，作为受体底物。在这里，我们报告（i）编码SgcC5同源物的基因在实验确认和生物信息学预测的烯二炔生物合成基因簇中广泛分布，形成了新的缩合酶进化枝，（ii）SgcC5与规范的缩合结构域共有相似的整体结构，但形式溶液中的同型二聚体，其活性位点位于空腔中，而不是通常在缩合结构域中看到的隧道；（iii）SgcC5的催化组氨酸激活2-羟基，而SgcC5中的氢键网络更优选受体底物的R-对映异构体，解释了SgcC2束缚的（S）-3-氯-5-羟基-β-酪氨酸和（R）-1-苯基-1,2-乙二醇在酸碱催化下。这些发现扩大了催化范围，并揭示了对缩合酶的结构和机理的新见解。

更新日期：2018-03-13

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