MacGurn Jason A, Raghavan Sridharan, Stanley Sarah A, Cox Jeffery S
Department of Microbiology and Immunology, University of California, San Francisco, CA 94143, USA.
Mol Microbiol. 2005 Sep;57(6):1653-63. doi: 10.1111/j.1365-2958.2005.04800.x.
The Snm secretion system is a crucial virulence determinant of Mycobacterium tuberculosis. Genes encoding all known components of this alternative secretion pathway are clustered at the same genetic locus, known as RD1. Here, we show that a mutant M. tuberculosis strain containing a transposon insertion in the Rv3615c gene, which is situated outside the RD1 locus, results in loss of Snm secretion. Complementation analysis revealed that both Rv3615c and the downstream gene Rv3614c are required for Snm secretion. Thus, we have renamed the two genes snm9 and snm10 respectively. The snm9::Tn mutant phenocopies bona fide snm mutants, exhibiting attenuation in mice, macrophage growth defects and failure to suppress cytokine induction. Furthermore, yeast two-hybrid analysis revealed a physical interaction between Snm10 and Snm7 (Rv3882c), suggesting that Snm10 may function in complex with other Snm proteins during secretion. Thus, snm9 and snm10 are the first genes located outside the RD1 locus identified as critical components of Snm secretion. These data indicate that Snm secretion consists of an elaborate network of interactions that likely arose from multiple duplication events during the evolution of M. tuberculosis.
Snm分泌系统是结核分枝杆菌的一个关键毒力决定因素。编码该替代性分泌途径所有已知组分的基因聚集在同一基因座，即RD1。在此，我们表明，在位于RD1基因座之外的Rv3615c基因中含有转座子插入的结核分枝杆菌突变株会导致Snm分泌丧失。互补分析表明，Snm分泌需要Rv3615c和下游基因Rv3614c。因此，我们分别将这两个基因重命名为snm9和snm10。snm9::Tn突变体模拟真正的snm突变体，在小鼠中表现出减毒、巨噬细胞生长缺陷以及无法抑制细胞因子诱导。此外，酵母双杂交分析揭示Snm10与Snm7（Rv3882c）之间存在物理相互作用，表明Snm10在分泌过程中可能与其他Snm蛋白形成复合物发挥作用。因此，snm9和snm10是首次在RD1基因座之外鉴定出的作为Snm分泌关键组分的基因。这些数据表明，Snm分泌由一个复杂的相互作用网络组成，该网络可能源于结核分枝杆菌进化过程中的多次重复事件。
