Centre National de la Recherche Scientifique UMR 9004, Institut de Recherche en Infectiologie de Montpellier (IRIM), Université de Montpellier, 1919 route de Mende, 34293 Montpellier, France.
INSERM, IRIM, 34293 Montpellier, France.
ACS Infect Dis. 2020 Oct 9;6(10):2756-2770. doi: 10.1021/acsinfecdis.0c00490. Epub 2020 Sep 14.
, an emerging pathogen responsible for severe lung infections in cystic fibrosis patients, displays either smooth (S) or rough (R) morphotypes. The S-to-R transition is associated with reduced levels of glycopeptidolipid (GPL) production and is correlated with increased pathogenicity in animal and human hosts. While the structure of GPL is well established, its biosynthetic pathway is incomplete. In addition, the biological functions of the distinct structural parts of this complex lipid remain elusive. Herein, the gene encoding a putative -methyltransferase was deleted in the S variant. Subsequent biochemical and structural analyses demonstrated that methoxylation of the fatty acyl chain of GPL was abrogated in the mutant, and this defect was rescued upon complementation with a functional gene. In contrast, the introduction of derivatives mutated at residues essential for methyltransferase activity failed to complement GPL defects, indicating that encodes an -methyltransferase. Unexpectedly, phenotypic analyses showed that was more hydrophilic than its parental progenitor, as demonstrated by hexadecane-aqueous buffer partitioning and atomic force microscopy experiments with hydrophobic probes. Importantly, the invasion rate of THP-1 macrophages by was reduced by 50% when compared to the wild-type strain. Together, these results indicate that Fmt -methylates the lipid moiety of GPL and plays a substantial role in conditioning the surface hydrophobicity of as well as in the early steps of the interaction between the bacilli and macrophages.
，一种新兴的病原体，可导致囊性纤维化患者肺部严重感染，表现为光滑（S）或粗糙（R）形态。S 到 R 的转变与糖肽脂（GPL）产生水平降低有关，并与动物和人类宿主中致病性增加相关。虽然 GPL 的结构已经确立，但它的生物合成途径并不完整。此外，这种复杂脂质的不同结构部分的生物学功能仍然难以捉摸。在此，编码假定的 -甲基转移酶的 基因在 S 变体中被缺失。随后的生化和结构分析表明，GPL 中脂肪酸链的甲氧基化在 突变体中被废除，并且该缺陷在与功能性 基因互补时得到挽救。相比之下，引入在对于甲基转移酶活性至关重要的残基处突变的 衍生物未能互补 GPL 缺陷，表明 编码 -甲基转移酶。出乎意料的是，表型分析表明，与亲本相比， 更亲水，如十六烷-水缓冲分配和带有疏水探针的原子力显微镜实验所示。重要的是，与野生型菌株相比，THP-1 巨噬细胞对 的入侵率降低了 50%。这些结果表明，Fmt 甲基化 GPL 的脂质部分，并在调节 的表面疏水性以及杆菌与巨噬细胞相互作用的早期步骤中发挥重要作用。
