Adenylate‐forming enzymes (AFEs) are a mechanistic superfamily of proteins that are involved in many cellular roles. In the biosynthesis of benzoxazole antibiotics, an AFE has been reported to play a key role in the condensation of cyclic molecules. In the biosynthetic gene cluster for the benzoxazole AJI9561, AjiA1 catalyzes the condensation of two 3‐hydroxyanthranilic acid (3‐HAA) molecules using ATP as a co‐substrate. Here, the enzymatic activity of AjiA1 is reported together with a structural analysis of its apo form. The structure of AjiA1 was solved at 2.0 Å resolution and shows a conserved fold with other AFE family members. AjiA1 exhibits activity in the presence of 3‐HAA (K_m = 77.86 ± 28.36, k_cat = 0.04 ± 0.004) and also with the alternative substrate 3‐hydroxybenzoic acid (3‐HBA; K_m = 22.12 ± 31.35, k_cat = 0.08 ± 0.005). The structure of AjiA1 in the apo form also reveals crucial conformational changes that occur during the catalytic cycle of this enzyme which have not been described for any other AFE member. Consequently, the results shown here provide insights into this protein family and a new subgroup is proposed for enzymes that are involved in benzoxazole‐ring formation.

中文翻译：

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AjiA1的晶体结构揭示了腺苷酸形成酶家族中一种新的结构运动机制

腺苷酸形成酶 (AFEs) 是蛋白质的机械超家族，涉及许多细胞作用。在苯并恶唑抗生素的生物合成中，据报道 AFE 在环状分子的缩合中起关键作用。在苯并恶唑 AJI9561 的生物合成基因簇中，AjiA1 使用 ATP 作为共底物催化两个 3-羟基邻氨基苯甲酸 (3-HAA) 分子的缩合。在这里，报告了 AjiA1 的酶活性及其 apo 形式的结构分析。AjiA1 的结构以 2.0 Å 分辨率解析，并显示出与其他 AFE 家族成员的保守折叠。AjiA1 在 3-HAA 存在下表现出活性 ( K _m  = 77.86 ± 28.36, k _cat= 0.04 ± 0.004）以及替代底物 3-羟基苯甲酸（3-HBA；K _m = 22.12 ± 31.35，k _cat = 0.08 ± 0.005）。apo 形式的 AjiA1 结构还揭示了在该酶催化循环期间发生的关键构象变化，这些变化尚未在任何其他 AFE 成员中得到描述。因此，此处显示的结果提供了对该蛋白质家族的见解，并为参与苯并恶唑环形成的酶提出了一个新的亚组。