Molecular Genetics and Cellular Microbiology, Institute for Molecular Biosciences, University of Frankfurt, Frankfurt, Germany.
Institute of Physical and Theoretical Chemistry, Goethe University, Frankfurt, Germany.
Appl Environ Microbiol. 2019 May 16;85(11). doi: 10.1128/AEM.00534-19. Print 2019 Jun 1.
Lantibiotics subtilin and nisin are produced by and , respectively. To prevent toxicity of their own lantibiotic, both bacteria express specific immunity proteins, called SpaI and NisI. In addition, ABC transporters SpaFEG and NisFEG prevent lantibiotic toxicity by transporting the respective peptides to the extracellular space. Although the three-dimensional structures of SpaI and NisI have been solved, very little is known about the molecular function of either lipoprotein. Using laser-induced liquid bead ion desorption (LILBID)-mass spectrometry, we show here that subtilin interacts with SpaI monomers. The expression of either SpaI or NisI in a subtilin-nonproducing strain resulted in the respective strain being more resistant against either subtilin or nisin. Furthermore, pore formation provided by subtilin and nisin was prevented specifically upon the expression of either SpaI or NisI. As shown with a nisin-subtilin hybrid molecule, the C-terminal part of subtilin but not any particular lanthionine ring was needed for SpaI-mediated immunity. With respect to growth, SpaI provided less immunity against subtilin than is provided by the ABC transporter SpaFEG. However, SpaI prevented pore formation much more efficiently than SpaFEG. Taken together, our data show the physiological function of SpaI as a fast immune response to protect the cellular membrane. The two lantibiotics nisin and subtilin are produced by and , respectively. Both peptides have strong antimicrobial activity against Gram-positive bacteria, and therefore, appropriate protection mechanisms are required for the producing strains. To prevent toxicity of their own lantibiotic, both bacteria express immunity proteins, called SpaI and NisI, and in addition, ABC transporters SpaFEG and NisFEG. Whereas it has been shown that the ABC transporters protect the producing strains by transporting the toxic peptides to the extracellular space, the exact mode of action and the physiological function of the lipoproteins during immunity are still unknown. Understanding the exact role of lantibiotic immunity proteins is of major importance for improving production rates and for the design of newly engineered peptide antibiotics. Here, we show (i) the specificity of each lipoprotein for its own lantibiotic, (ii) the specific physical interaction of subtilin with its lipoprotein SpaI, (iii) the physiological function of SpaI in protecting the cellular membrane, and (iv) the importance of the C-terminal part of subtilin for its interaction with SpaI.
细菌产生的细菌素 subtilin 和 nisin 分别由基因 和 编码。为了防止自身细菌素的毒性，两种细菌都表达了特定的免疫蛋白，分别称为 SpaI 和 NisI。此外，ABC 转运蛋白 SpaFEG 和 NisFEG 通过将各自的肽运输到细胞外空间来防止细菌素毒性。尽管已经解决了 SpaI 和 NisI 的三维结构，但对于这两种脂蛋白的分子功能知之甚少。使用激光诱导液珠离子解吸（LILBID）-质谱法，我们在这里表明 subtilin 与 SpaI 单体相互作用。在不产生 subtilin 的 菌株中表达 SpaI 或 NisI 都会导致相应的菌株对 subtilin 或 nisin 具有更强的抗性。此外，特异性表达 SpaI 或 NisI 可阻止 subtilin 和 nisin 形成孔。如用 nisin-subtilin 杂合分子所示，subtilin 的 C 端部分而不是任何特定的类硫醚环是 SpaI 介导免疫所必需的。就生长而言，SpaI 对 subtilin 的免疫作用不如 ABC 转运蛋白 SpaFEG。然而，SpaI 阻止孔形成的效率比 SpaFEG 高得多。总的来说，我们的数据表明 SpaI 的生理功能是作为一种快速的免疫反应来保护细胞膜。细菌素 nisin 和 subtilin 分别由 和 产生。这两种肽都对革兰氏阳性菌具有很强的抗菌活性，因此，产生菌需要适当的保护机制。为了防止自身细菌素的毒性，两种细菌都表达了免疫蛋白，分别称为 SpaI 和 NisI，此外，还有 ABC 转运蛋白 SpaFEG 和 NisFEG。虽然已经表明 ABC 转运蛋白通过将有毒肽运输到细胞外空间来保护产生菌，但脂蛋白在免疫过程中的确切作用模式和生理功能仍不清楚。了解细菌素免疫蛋白的确切作用对于提高产率和设计新的工程肽抗生素非常重要。在这里，我们表明：（i）每种脂蛋白对其自身细菌素的特异性；（ii）subtilin 与其脂蛋白 SpaI 的特异性物理相互作用；（iii）SpaI 在保护细胞膜方面的生理功能；（iv）subtilin 的 C 端部分对于其与 SpaI 的相互作用很重要。
