Structural and Functional Characterization of Extraintestinal Pathogenic Escherichia coli (ExPEC) PasTI complex Pubblico

Abstract

PasTI appears to be a novel type II toxin-antitoxin (TA) module found in Extraintestinal Pathogenic Escherichia coli (ExPEC) which is critical for ExPEC cell survival in kidneys (Norton and Mulvey 2012). PasT is a putative toxin protein that causes ExPEC growth arrest, whereas PasI is PasT’s cognate antitoxin which counteracts PasT’s toxic activities under normal growth conditions. The pasTI gene causes and enhances ExPEC persister cell formation upon exposure to antibiotics, nutrient starvation, oxidative and nitrosative stress conditions (Norton and Mulvey 2012). Colonization of ExPEC in extraintestinal environments causes biofilm-like communities to form resulting in antibiotic tolerance and causing an array of chronic human diseases such as urinary tract infections and meningitis (Norton and Mulvey 2012, Wiles, Norton et al. 2013). Escherichia coli (E. coli) RatA (also known as YfjG toxin), is a homologue of PasT toxin and binds to the 50S ribosomal subunit to block its association with 30S subunit (Zhang and Inouye 2011). This blockage inhibits the 70S formation and protein synthesis (Zhang and Inouye 2011). Due to the high sequence identity between PasT and RatA, I hypothesize PasT functions in a similar manner to inhibit ribosomal subunit association. This characterization is important for determining how PasT toxin interferes with vital cellular processes, identifying the binding site of the PasT protein on the ribosome, and studying its function. I also propose to solve the structure of the PasT toxin, PasI antitoxin and PasTI complex using x-ray crystallography, and to understand the function of the PasTI system and decipher the interaction between PasT and its bound ribosomal subunit.

Table of Contents

TABLE OF CONTENTS

Abstract ....................................................................................................................................................4

Motivation…………………………………………………………………………………………………………..7

Background …………………………………..……………………………………………………………….8-10

Scientific/ Technical Approach……………………………………………………………………………...10-11

Results and Conclusions....................................................................................................................11-14

Future Directions ...............................................................................................................................15-16

Experimental Methods.......................................................................................................................16-17

References ........................................................................................................................................17-19

Supplementary Data………………………………………………………………………………..............20-21

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School	Laney Graduate School
Department	Chemistry
Degree	M.S.
Submission	Master's Thesis
Language	English
Research Field	Chemistry, Biochemistry
Parola chiave	toxin-antitoxin
Committee Chair / Thesis Advisor	Christine Dunham, Emory University

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