The Novel Property of Heptapeptide of Microcin C7 in Affecting the Cell Growth of Escherichia coli.

Rensen Ran,Xia Xu,Huan Zeng,Dong Zhao,Ruiyuan Liu

doi:10.3390/molecules22030432

Abstract

Microcin C7 (McC), widely distributed in enterobacteria, is a promising antibiotic against antibiotic resistance. Previous studies have demonstrated that the heptapeptide of McC is only responsible for recognizing the inner membrane transporter YejABEF to deliver McC into microbial cells, but lacks the capacity for inhibiting microbial cell growth. In this study, the effect of the heptapeptide (MR) and two analogues, N-formylated heptapeptide (f-MR) and N-aceylated heptapeptide (a-MR), on microbial cell growth were examined. It is surprising to find that MR not only inhibits the activity of intracellular β-galactosidase, respiratory chain dehydrogenases, and 6-phosphogluconate dehydrogenases (6PGDH), but it is also able to inhibit Escherichia coli growth, and eventually leads to cell death at the lethal concentration of 5.34 mM within 10 min. The modification of MR results in a slight increase in the lethal concentration. Cell membrane integrity at the lethal concentration confirms that MR undergoes the inhibition effect, but not by destroying the cell membrane integrity. The novel property of MR provides a new insight into the Trojan horse strategy of McC and opens a new route for antibiotics design.

Highlights

Antibiotic resistance is a serious menace to global health in the 21st century [1], and may cause a death toll up to 10 million per year worldwide by 2050 [2]
In this study, we accidentally found that MR is able to kill bacterial at a high concentration, implicating that MR is a signal peptide for transporting Microcin C7 (McC) into cells but concentration, implicating that MR is a signal peptide for transporting McC into cells and has an ability to affect the growth of E. coli BL21, inconsistent with the previous study [15,16]
Fluoren-9-ylmethoxycarbonyl (Fmoc) amino acid derivatives with side-chain protections were purchased from the GL Biochem Co., Ltd. (Shanghai, China). 2-Nitrophenyl β-D-galactopyranoside (ONPG), oxidized nicotinamide adenine dinucleotide (NAD+ ), 6-phosphogluconate, iodonitrotetrazolium chloride (INT) and reagents for peptide synthesis were purchased from the Aladdin Industrial Corporation (Shanghai, China)

Summary

Introduction

Antibiotic resistance is a serious menace to global health in the 21st century [1], and may cause a death toll up to 10 million per year worldwide by 2050 [2]. As a promising antibiotic against antibiotic resistance [5], numerous efforts have been made to understand the mechanism behind the. McC antimicrobial activity [6,7]. McC is actively transported into cells by MR through interacting with the ABC transporter YejABEF [10,11]. McC is metabolized by the peptide deformylase and aminopeptidases to liberate an analogue of nonhydrolyzable aspartyl adenylate with a propylamine [12,13,14]. An adenosine triphosphate (ATP) and an aspartate (Asp) bind to the processed McC to inhibit aminoacylation of cognate tRNAAsp , leading to the blocking of protein synthesis and eventually resulting in cessation of translation and cell growth [15]

Methods

Results

Discussion

Conclusion