An Entirely Solid Phase Peptide Synthesis-Based Strategy for Synthesis of Gelatinase Biosynthesis-Activating Pheromone (GBAP) Analogue Libraries: Investigating the Structure–Activity Relationships of the Enterococcus faecalis Quorum Sensing Signal

Abstract

The development of an entirely solid-phase peptide synthesis-based synthesis of the quorum sensing signal gelatinase biosynthesis-activating pheromone (GBAP) from Enterococcus faecalis is reported. The method was used to prepare three libraries of analogues to investigate the structure-activity relationships (SARs) of the GBAP signal. The SAR studies revealed new characteristics of the GBAP signal and uncovered the most potent quorum sensing activator in E. faecalis known to date.

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

“…With an EC 50 value of 1.92 nM, it was comparably potent to native GBAP. This result reinforces the unique role the F7 position has in GBAP activity as this residue was found to be critical for activity (replacement with alanine resulted in a relatively inactive analog, GBAP-F7A, EC 50 > 1000 nM), 19 yet was also the site previously found to retain potency when its chirality was inverted or when a larger amino acid was substituted. 19,21 This is especially interesting since Phe7 is a potential cleavage site for degradation by chymotrypsin.…”

“…1,14,[16][17][18] We have previously investigated the relative importance of each of GBAP's residues on QS activation by modifying their functional groups (alanine scan) and chirality (D-amino acid scan). 19 Information gained from this earlier work, combined with work done by others, 20 enabled us to rationally design potent activators and inhibitors of the fsr QS circuit. 21 Although these investigations have resulted in a greatly increased understanding of the structure-activity relationships (SARs) involved in QS activation, additional questions remained.…”

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).…”

Development of a Dominant Negative Competence‐Stimulating Peptide (dnCSP) that Attenuates Streptococcus pneumoniae Infectivity in a Mouse Model of Acute Pneumonia

“…The QS circuitry is also involved in virulence factor production and biofilm formation, thus making the competence regulon an attractive target for attenuating pneumococcus infections, while at the same time, preventing the acquisition of antibiotic resistance genes. Moreover, because QS is not essential for bacterial growth, it has attracted significant attention over the past two decades as a potential anti‐infective target that places minimal selective pressure for the development of resistance against a multitude of bacterial pathogens . Two main CSP variants, CSP1 and CSP2, have been identified in pneumococcus, leading to two distinct pherotypes being classified (Figure ).…”