MRNA Interferase Bacillus cereus BC0266 Shows MazF-Like Characteristics Through Structural and Functional Study.

Sung-Min Kang,Ji Sung Koo,Chang-Min Kim,Do-Hee Kim,Bong-Jin Lee

doi:10.3390/toxins12060380

Sung-Min Kang, Ji Sung Koo + Show 3 more

Open Access

https://doi.org/10.3390/toxins12060380

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Journal: Toxins	Publication Date: Jun 8, 2020
Citations: 4	License type: CC BY 4.0

Affiliation: Seoul National University, Jeju National University

Abstract

Toxin–antitoxin (TA) systems are prevalent in bacteria and are known to regulate cellular growth in response to stress. As various functions related to TA systems have been revealed, the importance of TA systems are rapidly emerging. Here, we present the crystal structure of putative mRNA interferase BC0266 and report it as a type II toxin MazF. The MazF toxin is a ribonuclease activated upon and during stressful conditions, in which it cleaves mRNA in a sequence-specific, ribosome-independent manner. Its prolonged activity causes toxic consequences to the bacteria which, in turn, may lead to bacterial death. In this study, we conducted structural and functional investigations of Bacillus cereus MazF and present the first toxin structure in the TA system of B. cereus. Specifically, B. cereus MazF adopts a PemK-like fold and also has an RNA substrate-recognizing loop, which is clearly observed in the high-resolution structure. Key residues of B. cereus MazF involved in the catalytic activity are also proposed, and in vitro assay together with mutational studies affirm the ribonucleic activity and the active sites essential for its cellular toxicity.

Highlights

Toxin–antitoxin (TA) systems are prevalent in prokaryotes and function to regulate cellular growth in response to stress such as antibiotic exposure, nutrient starvation, heat shock, and DNA damage.Initially, TA systems were discovered as a part of the plasmid maintenance system, in which only the daughter cells harboring the vertically transferred TA operon can survive [1,2,3,4,5]
High-resolution (2.0 Å) structure was obtained by X-ray crystallography, and overall structural folding of B. cereus MazF indicated β-barrel arrangement containing two independent β-sheets identical to that of MazF toxins
Through comparison analysis with previously reported structures of MazFs, amino acid residues Arg25 and Thr48 in B. cereus MazF were well conserved with other MazFs and were confirmed as key residues in the catalytic activity of B

Summary

Introduction

Toxin–antitoxin (TA) systems are prevalent in prokaryotes and function to regulate cellular growth in response to stress such as antibiotic exposure, nutrient starvation, heat shock, and DNA damage.Initially, TA systems were discovered as a part of the plasmid maintenance system, in which only the daughter cells harboring the vertically transferred TA operon can survive [1,2,3,4,5]. Toxin–antitoxin (TA) systems are prevalent in prokaryotes and function to regulate cellular growth in response to stress such as antibiotic exposure, nutrient starvation, heat shock, and DNA damage. The TA systems are involved in many cellular processes, including cell growth, cell persistence, cell dormancy, biofilm formation, antibiotic resistance, DNA replication, translation, cell division, cell wall synthesis, and cell apoptosis [6,7,8,9,10,11]. TA systems are a two-component system, composed of a toxin and an antitoxin usually sharing the same operon. TA systems can be categorized into six phenotypes (I-VI) by the nature of each component and the regulatory mechanisms of the antitoxins to its cognate toxins. In the case of RNA antitoxins, direct inhibition of mRNA encoding toxins and protein toxins constitute the type I

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