Structural characterization of type II secretion system (T2SS) effectors of Acinetobacter baumannii

Author(s)

Yuri Rafael de Oliveira Silva

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2022-10-27

Examining board members

Andréa Dessen; Mário Tyago Murakami; Juliana Ferreira de Oliveira; Gustavo Fernando Mercaldi; Juliana Helena Costa Smetana

• Advisor: Andréa Dessen

Abstract

"Acinetobacter baumannii" is a Gram-negative pathogen responsible for thousands of hospital-acquired infections every year, and has been receiving much attention due to increasing rates of antibiotic resistance. The prevalence of multidrug resistant strains that are also resistant to disinfectant agents makes it difficult to eliminate this bacterium, and novel strategies are necessary to treat its infections. Its mechanisms of infection and toxicity are not as well characterized as in other pathogens, hindering the development of new treatments. The Type II Secretion System (T2SS) is one of the mechanisms involved in A. baumannii pathogenicity, being responsible for the translocation of proteins to the extracellular medium, including many virulence factors. Two lipases are secreted by this system, LipA and LipH, and although both have roles in bacterial virulence, they are still poorly characterized. LipA is from a family of lipases that depend on a foldase for activation, while LipH does not appear to depend on a partner to reach its final fold. The goal of this project was to characterize both lipases, LipA and LipH, to comprehend the mechanisms involved in LipA activation by the foldase LipB, and to study its interactions with the T2SS in the periplasm. We characterized the lipases through biophysics and biochemistry techniques, and propose that there could be synergy between the two enzymes. We also obtained the crystal structure of the complex between LipA and its foldase LipB from A. baumannii, the first structure of a complex between a family I.1 lipase in complex with its foldase. We identified residues that are important for the protein-protein interaction and proposed regions of the lipase affected during stabilization by LipB. The structural characterization of LipH was performed using computational modeling, and its structural characteristics were similar to lipases from other species. Finally, we have detected an inhibitory action of a T2SS component over the activity of LipA in complex with LipB. Our results may contribute to the development of anti-virulence strategies against A. baumannii and can possibly contribute for the area of lipase engineering for industrial purposes (AU)

• FAPESP's process: 18/04344-0 - Structural characterization of type II secretion system (T2SS) effectors of Acinetobacter baumannii
• Grantee: Yuri Rafael de Oliveira Silva
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)