In Gram-negative bacteria, N-terminal lipidation is a signal for protein trafficking from the inner membrane (IM) to the outer membrane (OM). The IM complex LolCDE extracts lipoproteins from the membrane and moves them to the chaperone LolA. The LolA-lipoprotein complex crosses the periplasm after which the lipoprotein is anchored to the OM. In γ-proteobacteria anchoring is assisted by the receptor LolB, while a corresponding protein has not been identified in other phyla. In light of the low sequence similarity between Lol-systems from different phyla and that they may use different Lol components, it is crucial to compare representative proteins from several species. Here we present a structure–function study of LolA and LolB from two phyla: LolA from Porphyromonas gingivalis (phylum bacteroidota), and LolA and LolB from Vibrio cholerae (phylum proteobacteria). Despite large sequence differences, the LolA structures are very similar, hence structure and function have been conserved throughout evolution. However, an Arg-Pro motif crucial for function in γ-proteobacteria has no counterpart in bacteroidota. We also show that LolA from both phyla bind the antibiotic polymyxin B whereas LolB does not. Collectively, these studies will facilitate the development of antibiotics as they provide awareness of both differences and similarities across phyla.

在革兰氏阴性菌中，N 末端脂化是蛋白质从内膜 (IM) 运输到外膜 (OM) 的信号。IM 复合物 LolCDE 从膜中提取脂蛋白并将它们移动到伴侣 LolA。LolA-脂蛋白复合物穿过周质，之后脂蛋白被锚定在 OM 上。在 γ-变形菌中，锚定由受体 LolB 辅助，而在其他门中尚未鉴定出相应的蛋白质。鉴于来自不同门的 Lol 系统之间的低序列相似性以及它们可能使用不同的 Lol 组件，比较来自几个物种的代表性蛋白质是至关重要的。在这里，我们展示了来自两个门的 LolA 和 LolB 的结构-功能研究：来自牙龈卟啉单胞菌的 LolA（拟杆菌门），以及来自霍乱弧菌（变形菌门）的 LolA 和 LolB。尽管存在很大的序列差异，但 LolA 的结构非常相似，因此结构和功能在整个进化过程中一直保持不变。然而，对 γ-变形菌功能至关重要的 Arg-Pro 基序在拟杆菌门中没有对应物。我们还表明，来自两个门的 LolA 都与抗生素多粘菌素 B 结合，而 LolB 则没有。总的来说，这些研究将促进抗生素的开发，因为它们提供了跨门的差异和相似性的认识。