Abstract
PPE represent a peculiar family of mycobacterial proteins characterized by a 180 aminoacids conserved N-terminal domain. Several PPE genes are co-transcribed with a gene encoding for a protein belonging to another family of mycobacterial specific proteins named PE. Only one PE-PPE couple has been extensively characterized so far (PE25-PPE41) and it was shown that these two proteins form a heterodimer and that this interaction is essential for PPE41 stability and translocation through the mycobacterial cell wall. In this study we characterize the PE11-PPE17 couple. In contrast with what was found for PE25-PPE41, we show that PPE17 is not secreted but surface exposed. Moreover, we demonstrate that the presence of PE11 is not necessary for PPE17 stability or for its localization on the mycobacterial surface. Finally, we show that the PPE domain of PPE17 targets the mycobacterial cell wall and that this domain can be used as a fusion partner to expose heterologous proteins on the mycobacterial surface.
Highlights
IntroductionThe members of these families are characterized from highly conserved N-terminal domains of about 110 or 180 aminoacids, respectively, typically containing the motif PE or PPE at the beginning of their amino acidic sequence, after which they are named [1]
One of the most intriguing features of the genomes of slow growing mycobacteria is the presence of a high number of genes encoding for members of two peculiar protein families named PE and PPE
In a recent study we showed that the catalytic domain of the secreted lipase LipY is fused to a PE domain in Mycobacterium tuberculosis, to a PPE domain in Mycobacterium marinum and to a canonical signal peptide in Mycobacterium gilvum, suggesting that these domains are interchangeable modules used by mycobacteria to target proteins to the bacterial surface [15]
Summary
The members of these families are characterized from highly conserved N-terminal domains of about 110 or 180 aminoacids, respectively, typically containing the motif PE or PPE at the beginning of their amino acidic sequence, after which they are named [1]. Secretion of several PE and PPE is dependent on the type VII secretion system ESX-5, the molecular mechanism of the transport process is still unknown [10,16].We reported that the PE domain of one of the better characterized PE proteins, PE_PGRS33, was able to drive the surface localization of MPT64 when it was fused at its C-terminus [12,13]. The expression of this chimeric protein on the surface of a recombinant Mycobacterium bovis BCG increased its protection against M. tuberculosis infection, opening the possibility to exploit the function of these proteins to develop an improved vaccine against tuberculosis [17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
