Center for Staphylococcal Research, Department of Pathology and Microbiology, University of Nebraska Medical Centergrid.266813.8, Omaha, Nebraska, USA.
Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, Kansas, USA.
mBio. 2021 Feb 22;13(1):e0282721. doi: 10.1128/mbio.02827-21. Epub 2022 Feb 1.
The Staphylococcus aureus and operons encode members of a well-conserved family of proteins thought to be involved in programmed cell death (PCD). Based on the structural similarities that CidA and LrgA share with bacteriophage holins, we have hypothesized that these proteins function by forming pores within the cytoplasmic membrane. To test this, we utilized a "lysis cassette" system that demonstrated the abilities of the and genes to support bacteriophage endolysin-induced cell lysis. Typical of holins, CidA- and LrgA-induced lysis was dependent on the coexpression of endolysin, consistent with the proposed holin-like functions of these proteins. In addition, the CidA and LrgA proteins were shown to localize to the surface of membrane vesicles and cause leakage of small molecules, providing direct evidence of their hole-forming potential. Consistent with recent reports demonstrating a role for the homologues in other bacterial and plant species in the transport of by-products of carbohydrate metabolism, we also show that is important for S. aureus to utilize pyruvate during microaerobic and anaerobic growth, by promoting the uptake of pyruvate under these conditions. Combined, these data reveal that the CidA and LrgA membrane proteins possess holin-like properties that play an important role in the transport of small by-products of carbohydrate metabolism. The Staphylococcus aureus and operons represent the founding members of a large, highly conserved family of genes that span multiple kingdoms of life. Despite the fact that they have been shown to be involved in bacterial PCD, very little is known about the molecular/biochemical functions of the proteins they encode. The results presented in this study reveal that the and genes encode proteins with bacteriophage holin-like functions, consistent with their roles in cell death. However, these studies also demonstrate that these operons are involved in the transport of small metabolic by-products of carbohydrate metabolism, suggesting an intriguing link between these two seemingly disparate processes.
金黄色葡萄球菌和操纵子编码一组高度保守的蛋白家族成员，这些蛋白被认为参与程序性细胞死亡（PCD）。基于 CidA 和 LrgA 与噬菌体 holin 共享的结构相似性，我们假设这些蛋白通过在细胞质膜中形成孔来发挥作用。为了验证这一点，我们利用了一个“裂解盒”系统，该系统证明了和基因能够支持噬菌体内溶素诱导的细胞裂解。与 holin 典型的是，CidA 和 LrgA 诱导的裂解依赖于内溶素的共表达，这与这些蛋白的拟 holin 样功能一致。此外，CidA 和 LrgA 蛋白被证明定位于膜泡的表面，并导致小分子泄漏，这为它们的孔形成潜力提供了直接证据。与最近的报道一致，这些报道表明在其他细菌和植物物种中，同源物在碳水化合物代谢副产物的运输中起作用，我们还表明，在微需氧和厌氧生长过程中，对于金黄色葡萄球菌利用丙酮酸是重要的，通过在这些条件下促进丙酮酸的摄取。综合这些数据表明，CidA 和 LrgA 膜蛋白具有拟 holin 样特性，在碳水化合物代谢副产物的运输中起着重要作用。金黄色葡萄球菌和操纵子代表了一个跨越多个生命王国的大型、高度保守的基因家族的创始成员。尽管已经表明它们参与了细菌 PCD，但对它们编码的蛋白的分子/生化功能知之甚少。本研究的结果表明，和基因编码具有噬菌体 holin 样功能的蛋白，这与它们在细胞死亡中的作用一致。然而，这些研究还表明，这些操纵子参与了碳水化合物代谢的小代谢副产物的运输，这表明这两个看似不同的过程之间存在着有趣的联系。
