Department of Cell Biology, Microbiology and Molecular Biology (CMMB), University of South Florida, Tampa, FL, USA.
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, USA.
Mol Microbiol. 2021 Aug;116(2):589-605. doi: 10.1111/mmi.14734. Epub 2021 Jun 14.
Surface proteins of Staphylococcus aureus play vital roles in bacterial physiology and pathogenesis. Recent work suggests that surface proteins are spatially regulated by a YSIRK/GXXS signal peptide that promotes cross-wall targeting at the mid-cell, though the mechanisms remain unclear. We previously showed that protein A (SpA), a YSIRK/GXXS protein and key staphylococcal virulence factor, mis-localizes in a ltaS mutant deficient in lipoteichoic acid (LTA) production. Here, we identified that SpA contains another cross-wall targeting signal, the LysM domain, which, in addition to the YSIRK/GXXS signal peptide, significantly enhances SpA cross-wall targeting. We show that LTA synthesis, but not LtaS, is required for SpA septal anchoring and cross-wall deposition. Interestingly, LTA is predominantly found at the peripheral cell membrane and is diminished at the septum of dividing staphylococcal cells, suggesting a restriction mechanism for SpA septal localization. Finally, we show that D-alanylation of LTA abolishes SpA cross-wall deposition by disrupting SpA distribution in the peptidoglycan layer without altering SpA septal anchoring. Our study reveals that multiple factors contribute to the spatial regulation and cross-wall targeting of SpA via different mechanisms, which coordinately ensures efficient incorporation of surface proteins into the growing peptidoglycan during the cell cycle.
金黄色葡萄球菌的表面蛋白在细菌生理学和发病机制中起着至关重要的作用。最近的研究表明，表面蛋白通过一种 YSIRK/GXXS 信号肽进行空间调节，该信号肽促进了在中细胞处的细胞壁交叉靶向，尽管其机制尚不清楚。我们之前曾表明，SpA（一种 YSIRK/GXXS 蛋白和关键的葡萄球菌毒力因子）在缺乏脂磷壁酸（LTA）产生的 ltaS 突变体中发生错误定位。在这里，我们鉴定出 SpA 包含另一个细胞壁交叉靶向信号，即 LysM 结构域，该结构域除了 YSIRK/GXXS 信号肽外，还显著增强了 SpA 的细胞壁交叉靶向。我们表明，LTA 合成而不是 LtaS 对于 SpA 隔膜锚定和细胞壁沉积是必需的。有趣的是，LTA 主要存在于细胞膜的外周部分，并且在分裂的葡萄球菌细胞的隔膜处减少，这表明 SpA 隔膜定位存在一种限制机制。最后，我们表明，LTA 的 D-丙氨酸化通过破坏肽聚糖层中的 SpA 分布而不是改变 SpA 隔膜锚定来破坏 SpA 的细胞壁沉积。我们的研究表明，多种因素通过不同的机制共同作用，对 SpA 的空间调节和细胞壁靶向进行调节，从而在细胞周期内确保表面蛋白有效地整合到不断增长的肽聚糖中。
