Substrate recognition by the mycobacterial type VII secretion systems


Mycobacterium tuberculosis strictly relies on type VII secretion systems (T7SSs) for its viability and to successfully infect host cells. These transport machineries mediate the transfer of proteins, many of them important virulence factors, across a highly impermeable cell envelope. M. tuberculosis has five homologous T7SSs, called ESX-1 to ESX-5, that mainly secrete members of three protein families, the Esx, PE/PPE and Esp proteins. The question is how these various substrates are specifically recognized by their cognate secretion systems, especially as multiple systems secrete related proteins in a system specific manner. We have recently identified a system specificity domain in PE/PPE substrates, recognized by the dedicated cytosolic chaperone EspG, and we used this knowledge to successfully redirect these substrates from one system to another (4). However, EspG only interacts with PE/PPE substrates, leaving the question how the other substrate families are specifically recognized. Here, we will elucidate the signals and factors that determine the system specific secretion of the different substrate classes. Both cytosolic interactions and recognition by EccC, the ATPase and substrate-binding subunit of the T7SS membrane channel, will be investigated using advanced genetic, molecular, biochemical and biophysical techniques. We will subsequently use this knowledge to redirect individual ESX-1 substrates and test the effect on virulence using macrophage and zebrafish infection models. Redirection of particularly these substrates is a powerful tool to analyze their individual roles in virulence, as this analysis has been seriously hindered by the fact that ESX-1 substrates are interdependent on each other for secretion.





Dr. E.N.G. Houben

Verbonden aan

Vrije Universiteit Amsterdam, Faculteit der Aard- en Levenswetenschappen, Moleculaire Microbiologie


01/01/2018 tot 31/12/2021


€ 298.544