Similarities and Differences between Colicin and Filamentous Phage Uptake by Bacterial Cells

Abstract

Gram-negative bacteria have evolved a complex envelope to adapt and survive in a broad range of ecological niches. This physical barrier is the first line of defense against noxious compounds and viral particles called bacteriophages. Colicins are a family of bactericidal proteins produced by and toxic to Escherichia coli and closely related bacteria. Filamentous phages have a complex structure, composed of at least five capsid proteins assembled in a long thread-shaped particle that protect the viral DNA. Despite their difference in size and complexity, group A colicins and filamentous phages both parasitize multiprotein complexes of their sensitive host for entry. They first bind to a receptor located at the surface of the target bacteria before specifically recruiting components of the Tol system to cross the outer membrane and find their way through the periplasm. The Tol system is thought to use the proton-motive force of the inner membrane to maintain outer membrane integrity during the life cycle of the cell. This review will describe the sequential docking mechanisms of group A colicins and filamentous phages during their uptake by their bacterial host, with a specific focus on the translocation step, promoted by interactions with the Tol system.

Bacterial Proteinaceous Compounds With Multiple Activities Toward Cancers and Microbial Infection

“…The structure of colicin proteins presents three domains; these are the receptor-binding domain responsible for target interaction, the N-terminal domain that mediates interaction with transporters, and the cytotoxic domain that allows antibacterial activity (Vasilchenko and Valyshev, 2019). Colicins act by binding to the outer membrane of integral membrane protein receptors, transporting the colicin to the inner membrane through Tol complex, inducing membrane depolarization, and degradation of DNA, ribosomal RNA, or tRNA (Duché and Houot, 2019) (Figure 3B). Colicins show activity on a wide bacterial range (Duché and Houot, 2019), and they also showed cytotoxic activity on breast carcinoma, fibrosarcoma, leiomyosarcoma, osteosarcoma, and colon carcinoma (Bandala et al, 2013; Karpinski and Adamczak, 2018).…”

“…Colicins act by binding to the outer membrane of integral membrane protein receptors, transporting the colicin to the inner membrane through Tol complex, inducing membrane depolarization, and degradation of DNA, ribosomal RNA, or tRNA (Duché and Houot, 2019) (Figure 3B). Colicins show activity on a wide bacterial range (Duché and Houot, 2019), and they also showed cytotoxic activity on breast carcinoma, fibrosarcoma, leiomyosarcoma, osteosarcoma, and colon carcinoma (Bandala et al, 2013; Karpinski and Adamczak, 2018). In this sense, a study using the different isolates of colicins, E1, E6, E7, K, and M, was evaluated against E. coli strains from patients with bacteraemia of urinary tract origin.…”

“…Among the proteins and peptides that act against bacterial and cancer cells, several stand out. Colicins act on a wide range of bacteria (Duché and Houot, 2019), and have also demonstrated activity against breast carcinoma, fibrosarcoma, leiomyosarcoma, osteosarcoma, and colon carcinoma (Karpinski and Adamczak, 2018). Another promising group is the nisins, which act on Gram-positive bacteria (Jack et al, 1995; Severina et al, 1998), and some nisin variations have demonstrated activity against Gram-negative bacteria (Kuwano et al, 2005), besides potent activity on HNSCC, reducing tumorigenesis (Joo et al, 2012).…”

The Peptidoglycan-associated lipoprotein Pal contributes to the virulence of Burkholderia mallei and provides protection against lethal aerosol challenge

“…Pal is a component of the Tol-Pal system, which comprises the five core proteins TolQ, TolR, TolA, TolB, and Pal. The Tol-Pal proteins form a complex that spans the inner and outer membranes and is required for maintaining cell wall integrity and can be exploited for the entry of macromolecules such as bacteriocins and bacteriophages [ 32 , 33 ]. The first amino acid of the mature Pal protein is a lipidated cysteine and the hydrophobic N-terminus anchors Pal in the outer membrane while the C-terminal region interacts with the meso-diaminopimelate residue of peptidoglycan in the periplasm.…”

“…The other components of the Tol-Pal system, TolQ and TolR, are located in the inner membrane and interact with TolA. Together, the Tol-Pal proteins form a cross-bridge between the outer membrane, peptidoglycan cell wall, and inner membrane [ 32 , 33 ].…”