SUMMARY

Many Gram-negative bacteria invade hosts and evade host cell defense systems by using virulence factors. These virulence factors are exported out of the cell via outer membrane proteins called autotransporters. The autotransporters are composed of the virulence-containing N-terminal passenger domain, and C-terminal translocon, which is folded by the beta-barrel assembly machinery (BAM) complex. The BAM complex is composed of five proteins from BamA to BamE. As an essential protein of the complex, BamA plays a key functional role in the folding and insertion of other outer membrane proteins, and it was shown experimentally that BamA may play a role in the passenger domain secretion of the autotransporters. However, no clear explanation behind such processes has been elucidated. In this proposal, I aim to address this problem by 1) resolving insertion and folding intermediates of the autotransporters EspP and YadA, 2) identifying the pathway of passenger domain secretion through BamA-autotransporter hybrid, and 3) determining the individual role of accessory proteins to the dynamics of BamA’s so-called lateral gate. By addressing these aims, I will uncover a mechanistic link connecting folding, insertion, and secretion of the passenger domain of autotransporters via the BAM complex.