N-Methylation of Amino Acids in Gelatinase Biosynthesis-Activating Pheromone Identifies Key Site for Stability Enhancement with Retention of the Enterococcus faecalis fsr Quorum Sensing Circuit Response

Abstract

The growing prevalence of multi-antibiotic-resistant bacteria necessitates looking at potential alternative approaches for attenuating infections by bacteria while reducing the rate of antibiotic resistance development. Enterococcus faecalis is responsible for a large percentage of clinical enterococci infections and its pathogenicity has been demonstrated to be influenced by quorum sensing (QS). In this study, we report the systematic study of the relationship between backbone hydrogens and the ability to activate the FsrC receptor. We demonstrate that N-methylation was particularly well-tolerated at one site (Phe7) and granted stability against protease digestion, increasing the peptide half-life relative to the native signal by more than 6-fold. The inclusion of the N-Me-Phe7 modification may be useful for improving the pharmacological properties of E faecalis QS inhibitors as part of the development of future therapeutic candidates.

Designing cyclic competence-stimulating peptide (CSP) analogs with pan-group quorum-sensing inhibition activity in Streptococcus pneumoniae

“…The fsr QS circuit in Enterococcus faecalis is another system that was explored for its therapeutic potential. Work by Murray and coworkers linked the fsr circuitry with biofilm formation and virulence factor production (48,49), and has sparked efforts to utilize the native signal, gelatinase biosynthesis-activating pheromone, as a scaffold for the development of QS modulators capable of lessening pathogenic phenotypes (50)(51)(52)(53). Lastly, the competence regulon was found to be a rather ubiquitous circuitry in streptococci, controlling the acquirement of genetic material from the environment, biofilm formation, bacteriocin production, and, in pathogenic streptococci, virulence factor production (39,54,55).…”

Attenuating the Streptococcus pneumoniae Competence Regulon Using Urea-Bridged Cyclic Dominant-Negative Competence-Stimulating Peptide Analogs

“…The successful construction of the linear peptide with alloc-protected amine groups at the 6th and 10th positions and an Fmoc-protected N -terminal was confirmed via mass spectrometry prior to cyclization. The alloc-protecting groups were removed using a previously reported protocol . Briefly, the resin was washed three times in DCM for 1 min.…”

Peptidomimetics as Potential Anti-Virulence Drugs Against Resistant Bacterial Pathogens

“…To investigate the best analog (Ac-GBAP-desQ1N2), an N -methyl scan was performed. Only the Ac-GBAP-Des(Q1N2)[ N -MeF7] analog showed similar agonistic activity ( McBrayer et al, 2019 ). Fortunately, for this system, some antagonistic candidates were developed ( Table 1 ).…”