A Short Peptide Derived from the ZorO Toxin Functions as an Effective Antimicrobial.

Otsuka Otsuka,Takahashi Takahashi,Masuda Masuda,Ishikawa Ishikawa

doi:10.3390/toxins11070392

Otsuka Otsuka, Takahashi Takahashi + Show 2 more

Open Access

https://doi.org/10.3390/toxins11070392

Copy DOI

Journal: Toxins	Publication Date: Jul 4, 2019
Citations: 10	License type: CC BY 4.0

Affiliation: Saitama University, Dokkyo Medical University

Abstract

Antimicrobial peptides are potential molecules for the development of novel antibiotic agents. The ZorO toxin of a type I toxin–antitoxin system in Escherichia coli O157:H7 is composed of 29 amino acids and its endogenous expression inhibits E. coli growth. However, little is known about its inhibitory mechanism. In this study, we demonstrate that the ZorO localized in the inner membrane affects the plasma membrane integrity and potential when expressed in E. coli cells, which triggers the production of cytotoxic hydroxyl radicals. We further show that five internal amino acids (Ala–Leu–Leu–Arg–Leu; ALLRL) of ZorO are necessary for its toxicity. This result prompted us to address the potential of the synthetic ALLRL peptide as an antimicrobial. Exogenously-added ALLRL peptide to Gram-positive bacteria, Staphylococcus aureus and Bacillus subtilis, and a fungus, Candida albicans, trigger cell membrane damage and exhibit growth defect, while having no effect on Gram-negative bacterium, E. coli. The ALLRL peptide retains its activity under the physiological salt concentrations, which is in contrast to natural antimicrobial peptides. Importantly, this peptide has no toxicity against mammalian cells. Taken together, an effective and short peptide, ALLRL, would be an attractive antimicrobial to Gram-positive bacteria and C. albicans.

Highlights

Antibiotic resistance remains a serious threat to human health and there is an urgent need for novel antimicrobial compounds with unique functional mechanisms
To elucidate the mechanism of the ZorO toxicity, ZorO was expressed in E. coli K12 TY0807 cells
When ZorO expressed in E. coli cells, it localized to the inner membrane (Figure 1C) and induced cell membrane depolarization (Figure 1D)

Summary

Introduction

Antibiotic resistance remains a serious threat to human health and there is an urgent need for novel antimicrobial compounds with unique functional mechanisms. Antimicrobial peptides target microbial cell membranes [1,3]. Because the compositions of cell membranes substantially differ between prokaryotes and eukaryotes, antimicrobial peptides display highly selective toxicity. These peptides are less likely to promote resistance, as alterations of the lipid composition of cell membranes are often toxic to bacteria. These advantages have led to the development of therapeutic antimicrobial peptides [4], there are disadvantages that need to be overcome. Many peptides unfold and lose their antimicrobial activity in Toxins 2019, 11, 392; doi:10.3390/toxins11070392 www.mdpi.com/journal/toxins

Methods

Results

Conclusion