Proteolytic Activity of Escherichia coli Oligopeptidase B Against Proline-Rich Antimicrobial Peptides

Abstract

Oligopeptidase B (OpdB) is a serine peptidase widespread among bacteria and protozoa that has emerged as a virulence factor despite its function has not yet been precisely established. By using an OpdB-overexpressing Escherichia coli strain, we found that the overexpressed peptidase makes the bacterial cells specifically less susceptible to several proline-rich antimicrobial peptides known to penetrate into the bacterial cytosol, and that its level of activity directly correlates with the degree of resistance. We established that E. coli OpdB can efficiently hydrolyze in vitro cationic antimicrobial peptides up to 30 residues in length, even though they contained several prolines, shortening them to inactive fragments. Two consecutive basic residues are a preferred cleavage site for the peptidase. In the case of a single basic residue, there is no cleavage if proline residues are present in the P1 and P2 positions. These results also indicate that cytosolic peptidases may cause resistance to antimicrobial peptides that have an intracellular mechanism of action, such as the proline-rich peptides, and may contribute to define the substrate specificity of the E. coli OpdB.

Antimicrobial and Immunomodulatory Activities of PR-39 Derived Peptides

“…For example, the secreted proteases aurelysin, V8 and Staphopain A &B are all involved in evasion of complement [36]. Another indication that protease activity could affect susceptibility towards PR-AMPs was recently described [37]. In this study, E. coli oligopeptidase effectively cleaved several PR-AMPs and overexpression of this protease resulted in increased resistance towards PR-AMPs.…”

Search for Shorter Portions of the Proline‐Rich Antimicrobial Peptide Fragment Bac5(1–25) That Retain Antimicrobial Activity by Blocking Protein Synthesis

“…This observation suggests that 16-17 residues could represent al ength threshold for the activity of mammalian PrAMPs. [17] Although OpdB likely represents a( weak) resistance mechanism against PrAMPs, [17] the intracellular cleavage of PrAMPs in some cases could release fragments that are as active as (or even more active than) their longer form, that could concurink illing pathogens. [4b] The study of mammalian PrAMP fragments is not limited to drug development, because shortened forms also occur in nature.…”

“…Interestingly,afew digestion products of this peptide resemble some fragments tested in the currentw ork. [17] Although OpdB likely represents a( weak) resistance mechanism against PrAMPs, [17] the intracellular cleavage of PrAMPs in some cases could release fragments that are as active as (or even more active than) their longer form, that could concurink illing pathogens.…”

D-BMAP18 Antimicrobial Peptide Is Active In vitro, Resists to Pulmonary Proteases but Loses Its Activity in a Murine Model of Pseudomonas aeruginosa Lung Infection

“…BMAP27(1–18) was selected for its good antimicrobial potential and reduced pulmonary toxicity, but its protective effect against P. aeruginosa lung infection in mice was scarce due to its rapid degradation in the pulmonary environment (Mardirossian et al, 2016). Proteolytic digestion is a problem that BMAP27(1–18) shared with many other native (Moncla et al, 2011; Mattiuzzo et al, 2014) and synthetic (Kim et al, 2014) antimicrobial peptides, reported also in the pulmonary environment (Sajjan et al, 2001; Morris et al, 2012). The use of enantiomeric all D -peptides represented a promising strategy to avoid proteolysis in lungs (Sajjan et al, 2001) and could possibly enhance BMAP27(1–18) antibacterial activity in vivo , reducing its degradation in the pulmonary environment.…”