Antibacterial toxin colicin N and phage protein G3p compete with TolB for a binding site on TolA

Abstract

Most colicins kill Escherichia coli cells by membrane pore formation or nuclease activity and, superficially, the mechanisms are similar: receptor binding, translocon recruitment, periplasmic receptor binding and membrane insertion. However, in detail, they employ a wide variety of molecular interactions that reveal a high degree of evolutionary diversification. Group A colicins bind to members of the TolQRAB complex in the periplasm and heterotrimeric complexes of colicin–TolA–TolB have been observed for both ColA and ColE9. ColN, the smallest and simplest pore-forming colicin, binds only to TolA and we show here that it uses the binding site normally used by TolB, effectively preventing formation of the larger complex used by other colicins. ColN binding to TolA was by β-strand addition with a KD of 1 µM compared with 40 µM for the TolA–TolB interaction. The β-strand addition and ColN activity could be abolished by single proline point mutations in TolA, which each removed one backbone hydrogen bond. By also blocking TolA–TolB binding these point mutations conferred a complete tol phenotype which destabilized the outer membrane, prevented both ColA and ColE9 activity, and abolished phage protein binding to TolA. These are the only point mutations known to have such pleiotropic effects and showed that the TolA–TolB β-strand addition is essential for Tol function. The formation of this simple binary ColN–TolA complex provided yet more evidence of a distinct translocation route for ColN and may help to explain the unique toxicity of its N-terminal domain.

Cyclic AMP-CRP Modulates the Cell Morphology of Klebsiella pneumoniae in High-Glucose Environment

“…RcsF functions in the signal transduction from the cell surface to Rcs signaling system (Castanie-Cornet et al, 2006;Sato et al, 2017), while OmpA, which acts as an outer membrane (OM) porin, can form channels through the cellular membranes (Hong et al, 2006). TolB plays a role in OM invagination during cell constriction in the trans-envelope Tol-pal system (Zhuang et al, 2002;Gerding et al, 2007;Ridley and Lakey, 2015). The Fts opera, containing FtsA, FtsI, FtsL, and FtsQ, are involved in cell division (Chen and Beckwith, 2001;Kureisaite-Ciziene et al, 2018;Du et al, 2019).…”

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

“…First, point mutations or deletions in tolA differentially affect colicin import; some remain active, whereas others lose their ability to kill mutated strains (59,89). Second, structural data have shown that the colicin A T-domain interacts with the convex site of TolAIII, whereas the phage Ff and IF1 pIII-N1 domain and colicin N T-domain bind to the concave side of TolAIII (18,21,(90)(91)(92)(93) (Fig. 1B).…”

Antibacterial Activity of Synergistic Effect of Colicin and Gold Nanoparticles Against Pseudomonas Aerugensa

“…The colicins produced by some isolates of E.coli are effective against many species of Gram negative and some Gram positive bacteria [31]. The agreement study was reported that the colicin had the ability of inhibiting the growth of one or more species and/or strains of pathogenic Enterobacteriaceae [32].…”