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 M. tuberculosis. In addition, pathogenicity of M. marinum is reduced in the ΔpecA mutant, indicating that PecA contributes to virulence.
Pathogenic mycobacteria, such
Mycobacterium tuberculosis
and
Mycobacterium marinum
, use a type VII secretion system (T7SS) subtype, called ESX-1, to mediate intracellular survival via phagosomal rupture and subsequent translocation of the
mycobacterium
to the host cytosol. Identifying the ESX-1 substrate that is responsible for this process is problematic because of the intricate network of codependent secretion between ESX-1 substrates.
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