Centro de Patogénese Molecular, Unidade dos Retrovirus e Infecções Associadas, Faculdade de Farmácia, Universidade de Lisboa, Lisboa, Portugal.
Mol Microbiol. 2010 Aug;77(3):672-86. doi: 10.1111/j.1365-2958.2010.07239.x. Epub 2010 Jun 1.
Like most double-stranded (ds) DNA phages, mycobacteriophage Ms6 uses the holin-endolysin system to achieve lysis of its host. In addition to endolysin (lysA) and holin (hol) genes, Ms6 encodes three accessory lysis proteins. In this study we investigated the lysis function of Gp1, which is encoded by the gp1 gene that lies immediately upstream of lysA. Escherichia coli lysis was observed after coexpression of LysA and Gp1 in the absence of Ms6 holin. Gp1 does not belong to the holin class of proteins, and we provide evidence that it shares several characteristics with molecular chaperones. We show that Gp1 interacts with LysA, and that this interaction is necessary for LysA delivery to its target. In addition, PhoA fusions showed that, in Mycobacterium smegmatis, LysA is exported to the extracytoplasmic environment in the presence of Gp1. We also show that Gp1 is necessary for efficient M. smegmatis lysis, as Ms6 gp1 deletion results in host lysis defects. We propose that delivery of Ms6 endolysin to the murein layer is assisted by Gp1, a chaperone-like protein, in a holin-independent manner.
像大多数双链 (ds) DNA 噬菌体一样，分枝杆菌噬菌体 Ms6 使用溶菌酶系统来实现对宿主的裂解。除了溶菌酶 (lysA) 和溶素基因 (hol) 外，Ms6 还编码三个辅助溶菌蛋白。在这项研究中，我们研究了由 lysA 上游的 gp1 基因编码的 Gp1 的溶菌功能。在没有 Ms6 溶素的情况下，共表达 LysA 和 Gp1 后，观察到大肠杆菌裂解。Gp1 不属于溶素类蛋白，我们提供的证据表明它与分子伴侣具有几个共同特征。我们表明 Gp1 与 LysA 相互作用，并且这种相互作用对于 LysA 递送到其靶标是必需的。此外，PhoA 融合表明，在耻垢分枝杆菌中，存在 Gp1 时，LysA 被输出到细胞外环境。我们还表明，Gp1 对于有效的 M. smegmatis 裂解是必需的，因为 Ms6 gp1 缺失导致宿主裂解缺陷。我们提出，Gp1 以溶素非依赖性方式辅助 Ms6 溶素递送到肽聚糖层。
