Department of Chemistry, University of Illinois at Urbana-Champaign, Champaign, IL, USA.
Department of Biochemistry, University of Illinois at Urbana-Champaign, Champaign, IL, USA.
Nat Chem Biol. 2018 Oct;14(10):928-933. doi: 10.1038/s41589-018-0122-4. Epub 2018 Sep 3.
Duramycin is a heavily post-translationally modified peptide that binds phosphatidylethanolamine. It has been investigated as an antibiotic, an inhibitor of viral entry, a therapeutic for cystic fibrosis, and a tumor and vasculature imaging agent. Duramycin contains a β-hydroxylated Asp (Hya) and four macrocycles, including an essential lysinoalanine (Lal) cross-link. The mechanism of Lal formation is not known. Here we show that Lal is installed stereospecifically by DurN via addition of Lys19 to a dehydroalanine. The structure of DurN reveals an unusual dimer with a new fold. Surprisingly, in the structure of duramycin bound to DurN, no residues of the enzyme are near the Lal cross-link. Instead, Hya15 of the substrate makes interactions with Lal, suggesting it acts as a base to deprotonate Lys19 during catalysis. Biochemical data suggest that DurN preorganizes the reactive conformation of the substrate, such that the Hya15 of the substrate can serve as the catalytic base for Lal formation.
达柔霉素是一种经过大量翻译后修饰的肽，可与磷脂酰乙醇胺结合。它已被研究作为抗生素、病毒进入抑制剂、囊性纤维化治疗剂以及肿瘤和血管成像剂。达柔霉素含有β-羟基化的天冬氨酸（Hya）和四个大环，包括必需的赖氨酰丙氨酸（Lal）交联。Lal 形成的机制尚不清楚。在这里，我们表明 Lal 是由 DurN 通过赖氨酸 19 加成到脱羟丙氨酸上立体特异性安装的。DurN 的结构揭示了一种具有新折叠的不寻常二聚体。令人惊讶的是，在与 DurN 结合的达柔霉素结构中，酶的没有残基靠近 Lal 交联。相反，底物的 Hya15 与 Lal 相互作用，表明它在催化过程中充当将赖氨酸 19 去质子化的碱基。生化数据表明，DurN 预先组织了底物的反应构象，使得底物的 Hya15 可以作为 Lal 形成的催化碱。
