The bioconjugation of proteins with small molecules has proved an invaluable strategy for probing and perturbing biological mechanisms. The general use of chemical methods for protein functionalisation can be limited however by the requirement for complicated reaction partners to be present in large excess, and harsh conditions which are incompatible with many protein scaffolds. Herein we describe a site-selective organocatalyst-mediated protein aldol ligation (OPAL) that affords stable carbon–carbon linked bioconjugates at neutral pH. OPAL enables rapid modification of proteins using simple aldehyde probes in minimal excess, and is utilised here in the affinity tagging of proteins in cell lysate. Furthermore we demonstrate that the β-hydroxy aldehyde OPAL product can be functionalised again at neutral pH in a tandem organocatalyst-mediated oxime ligation. This tandem strategy is showcased in the ‘chemical mimicry’ of a previously inaccessible natural dual post-translationally modified protein integral to the pathogenesis of the neglected tropical disease Leishmaniasis.

中文翻译：

---

使用有机催化剂介导的交叉羟醛键合连接在中性pH下对蛋白质进行选择性C-C修饰†

蛋白质与小分子的生物缀合已被证明是探索和扰动生物学机制的宝贵策略。然而，由于需要大量过量存在的复杂反应伙伴以及与许多蛋白质支架不相容的苛刻条件，因此化学方法用于蛋白质功能化的一般用途可能受到限制。在本文中，我们描述了一种在中性pH值下提供稳定的碳-碳连接生物缀合物的位点选择性有机催化剂介导的蛋白羟醛连接（OPAL）。OPAL允许使用简单的醛探针以最小的过量快速修饰蛋白质，并在此处用于细胞裂解液中蛋白质的亲和标记。此外，我们证明，β-羟基醛OPAL产物可以在中性pH下在串联有机催化剂介导的肟连接中再次官能化。这种串联策略在被忽视的热带病利什曼病的发病机理中不可或缺的天然双翻译后修饰蛋白的“化学模仿”中得以展示。