Structural and Functional Characterization of Legionella&nbsp;pneumophila Effector MavL.

Kevin Voth,Rachelia R Wibawa,Engku Nuraishah Huda E Zainudin,Miroslaw Cygler,Shivani Pasricha,Ivy Yeuk Wah Chung,Elizabeth L Hartland

doi:10.3390/biom11121802

Abstract

Legionella pneumophila is a Gram-negative intracellular pathogen that causes Legionnaires’ disease in elderly or immunocompromised individuals. This bacterium relies on the Dot/Icm (Defective in organelle trafficking/Intracellular multiplication) Type IV Secretion System (T4SS) and a large (>330) set of effector proteins to colonize the host cell. The structural variability of these effectors allows them to disrupt many host processes. Herein, we report the crystal structure of MavL to 2.65 Å resolution. MavL adopts an ADP-ribosyltransferase (ART) fold and contains the distinctive ligand-binding cleft of ART proteins. Indeed, MavL binds ADP-ribose with Kd of 13 µM. Structural overlay of MavL with poly-(ADP-ribose) glycohydrolases (PARGs) revealed a pair of aspartate residues in MavL that align with the catalytic glutamates in PARGs. MavL also aligns with ADP-ribose “reader” proteins (proteins that recognize ADP-ribose). Since no glycohydrolase activity was observed when incubated in the presence of ADP-ribosylated PARP1, MavL may play a role as a signaling protein that binds ADP-ribose. An interaction between MavL and the mammalian ubiquitin-conjugating enzyme UBE2Q1 was revealed by yeast two-hybrid and co-immunoprecipitation experiments. This work provides structural and molecular insights to guide biochemical studies aimed at elucidating the function of MavL. Our findings support the notion that ubiquitination and ADP-ribosylation are global modifications exploited by L. pneumophila.

Highlights

Legionella pneumophila is the causative agent of a life-threatening pneumonia calledLegionnaires’ disease
X-ray crystallography has already expanded our knowledge of L. pneumophila pathogenesis, by revealing many effectors that harbor eukaryotic-like folds and interfere with the host using molecular mimicry [3]
A characteristic of L. pneumophila effector proteins is their translocation into the host cell via the Dot/Icm secretion system

Summary

Introduction

Legionella pneumophila is the causative agent of a life-threatening pneumonia calledLegionnaires’ disease. Legionella pneumophila is the causative agent of a life-threatening pneumonia called. By infecting a broad range of protozoa in the environment, L. pneumophila has acquired distinct but overlapping mechanisms of virulence that rely on over 300 secreted effector proteins [1]. Arriving at a functional understanding of each of these effectors is hindered by the redundancy of their actions in the host cell [2], but is essential to provide insights into how L. pneumophila usurps host defenses. X-ray crystallography has already expanded our knowledge of L. pneumophila pathogenesis, by revealing many effectors that harbor eukaryotic-like folds and interfere with the host using molecular mimicry [3]. Structural data are especially useful in cases where the effector in question is functionally redundant, and knockout L. pneumophila mutants do not give rise to a phenotype.

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