Department of Chemistry, Stanford University, Stanford, California 94305, United States.
Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States.
J Am Chem Soc. 2024 Feb 14;146(6):4212-4220. doi: 10.1021/jacs.3c13670. Epub 2024 Jan 31.
The genomes of 40 strains of , most of which were associated with life-threatening human infections, encode a highly conserved assembly line polyketide synthase designated as the NOCAP (NOCardiosis-Associated Polyketide) synthase, whose product structure has been previously described. Here we report the structure and inferred biosynthetic pathway of the fully decorated glycolipid natural product. Its structure reveals a fully substituted benzaldehyde headgroup harboring an unusual polyfunctional tail and an O-linked disaccharide comprising a 3-α-epimycarose and 2--methyl-α-rhamnose whose installation requires flavin monooxygenase-dependent hydroxylation of the polyketide product. Production of the fully decorated glycolipid was verified in cultures of two patient-derived species. In both and spp., the glycolipid was only detected in culture supernatants, consistent with data from genetic knockout experiments implicating roles for two dedicated proteins in installing the second sugar substituent only after the monoglycosyl intermediate is exported across the bacterial cell membrane. With the NOCAP product in hand, the stage is set for investigating the evolutionary benefit of this polyketide biosynthetic pathway for strains capable of infecting human hosts.
40 株 的基因组，其中大多数与危及生命的人类感染有关，编码一种高度保守的装配线聚酮合酶，称为 NOCAP（非心内膜炎相关聚酮）合酶，其产物结构先前已有描述。在这里，我们报告了完全修饰的糖脂天然产物的结构和推断的生物合成途径。其结构揭示了一个完全取代的苯甲醛头基，带有不寻常的多功能尾部和一个 O 连接的二糖，由 3-α-表半乳辛糖和 2--甲基-α-鼠李糖组成，其安装需要黄素单加氧酶依赖性的聚酮产物羟化。在两种患者来源的 种的培养物中证实了完全修饰的糖脂的产生。在 和 spp. 中，糖脂仅在培养上清液中检测到，与基因敲除实验的数据一致，这些实验表明，只有在单糖基中间产物跨细菌细胞膜输出后，两种专用蛋白才能发挥作用，安装第二个糖取代基。有了 NOCAP 产物，就可以研究这种聚酮生物合成途径对能够感染人类宿主的 菌株的进化优势。
