Structural study of the substrate delivery mechanism of the type II secretion system of Acinetobacter baumannii

Abstract

Most bacteria rely on the secretion of proteins to adapt and survive in the environment. This is also true for pathogens, which secrete virulence factors to colonize and stablish infections in their hosts. The Gram-negative pathogen Acinetobacter baumannii is an example, since it uses its Type II Secretion System (T2SS) to secrete enzymes that assist in nutrient acquisition and modulation of host responses. During the execution of my PhD project, I have already cloned, developed expression and purification protocols, and partially characterized one of these enzymes in complex with its cognate chaperone.Although the general architecture and mechanism of T2SS are extensively studied, it is not clear how substrates are recognized and recruited by this system. Until now, interaction studies were performed and gave insights regarding which system components contact the substrate during secretion, but no structural data has been published. We believe tackling this question using X-ray crystallography and cryo-electron microscopy of complexes between system components and substrates might help us elucidate the recognition step of Type II secretion in Acinetobacter baumannii and would shed light on the comprehension of this step in other species.My project is part of a São Paulo Excellence Chair award received by my supervisor, Dr. Andréa Dessen, who directs 2 laboratories, one at LNBio/CNPEM, in Campinas (Brazil) and one at the IBS, in Grenoble (France). The laboratories and facilities in Grenoble have experience and established platforms to produce both soluble and membrane proteins, the latter notably through the use of cell-free expression systems. Moreover, I will have the opportunity to learn from expert X-ray crystallographers and cryo-electron microscopists who have been collaborating with our group for years. Thus, receiving this BEPE fellowship would be a great addition for my PhD project and for my career. (AU)