Amsterdam UMC, Vrije Universiteit Amsterdam, Medical Microbiology and Infection Control, Cancer Center Amsterdam, Amsterdam, Netherlands.
Amsterdam UMC, Vrije Universiteit Amsterdam, Medical Microbiology and Infection Control, Amsterdam Institute of Infection & Immunity, Amsterdam, Netherlands.
mBio. 2019 Oct 29;10(5):e01951-19. doi: 10.1128/mBio.01951-19.
Tuberculosis, one of the world's most severe infectious diseases, is caused by A major weapon of this pathogen is a unique cell wall that protects the pathogen from eradication by the immune system. Mycobacteria have specialized secretion systems, e.g., type VII secretion or ESX systems, to transport substrates across this cell wall. The largest group of proteins that are secreted by these ESX systems are the PE proteins. Previously, it was shown that the N-terminal PE domain of about 100 amino acids is required for secretion. Here, we describe the identification of an aspartic protease, designated PecA, that removes (part of) this PE domain at the cell surface. Nearly all of the observed PE_PGRS proteins are processed by PecA. Interestingly, the protease itself is also a secreted PE protein and subject to self-cleavage. Furthermore, a defect in surface processing has no effect on the activity of the PE lipase protein LipY but does seem to affect the functioning of other virulence factors, as a mutant strain of shows moderate attenuation in zebrafish larvae. In conclusion, our results reveal the presence of a functional aspartic acid protease in that cleaves LipY, itself as well as other members of the PE_PGRS family. Finally, mutants lacking PecA show growth attenuation , suggesting that PecA plays a role during infection. Aspartic proteases are common in eukaryotes and retroviruses but are relatively rare among bacteria (N. D. Rawlings and A. Bateman, BMC Genomics 10:437, 2009, https://doi.org/10.1186/1471-2164-10-437). In contrast to eukaryotic aspartic proteases, bacterial aspartic proteases are generally located in the cytoplasm. We have identified a surface-associated mycobacterial aspartic protease, PecA, which cleaves itself and many other type VII secretion substrates of the PE_PGRS family. PecA is present in most pathogenic mycobacterial species, including In addition, pathogenicity of is reduced in the mutant, indicating that PecA contributes to virulence.
结核病是世界上最严重的传染病之一，由结核分枝杆菌引起。这种病原体的主要武器之一是一种独特的细胞壁，它可以保护病原体免受免疫系统的清除。分枝杆菌具有专门的分泌系统，例如 VII 型分泌系统或 ESX 系统，以将底物运输穿过细胞壁。这些 ESX 系统分泌的最大蛋白质组是 PE 蛋白。以前已经表明，大约 100 个氨基酸的 N 端 PE 结构域是分泌所必需的。在这里，我们描述了一种天冬氨酸蛋白酶 PecA 的鉴定，该酶可在细胞表面去除（部分）该 PE 结构域。几乎所有观察到的 PE_PGRS 蛋白都被 PecA 加工。有趣的是，该蛋白酶本身也是一种分泌的 PE 蛋白，并进行自我切割。此外，表面处理缺陷对 PE 脂肪酶蛋白 LipY 的活性没有影响，但似乎会影响其他毒力因子的功能，因为 突变株在斑马鱼幼虫中表现出中度衰减。总之，我们的结果表明，在 中存在一种功能性天冬氨酸蛋白酶 PecA，可切割 LipY 及其自身以及 PE_PGRS 家族的其他成员。最后，缺乏 PecA 的突变体显示出生长衰减，表明 PecA 在感染过程中发挥作用。天冬氨酸蛋白酶在真核生物和逆转录病毒中很常见，但在细菌中相对较少（N.D. Rawlings 和 A. Bateman，BMC Genomics 10:437, 2009, https://doi.org/10.1186/1471-2164-10-437）。与真核天冬氨酸蛋白酶不同，细菌天冬氨酸蛋白酶通常位于细胞质中。我们已经鉴定出一种位于表面的分枝杆菌天冬氨酸蛋白酶 PecA，它可以切割自身和许多其他 VII 型分泌底物的 PE_PGRS 家族。PecA 存在于大多数致病性分枝杆菌物种中，包括 。此外， 突变体的致病性降低，表明 PecA 有助于毒力。
