Harnessing Multiple, Nonproteogenic Substitutions to Optimize CSP:ComD Hydrophobic Interactions in Group 1 Streptococcus pneumoniae

Abstract

Streptococcus pneumoniae (pneumococcus) is a human pathobiont that causes drastic antibiotic‐resistant infections and is responsible for millions of deaths universally. Pneumococcus pathogenicity relies on the competence‐stimulating peptide (CSP)‐mediated quorum‐sensing (QS) pathway that controls competence development for genetic transformation and, consequently, the spread of antibiotic resistance and virulence genes. Modulation of QS in S. pneumoniae can therefore be used to enervate pneumococcal infectivity as well as minimize the susceptibility to resistance development. In this work, we sought to optimize the interaction of CSP1 with its cognate transmembrane histidine kinase receptor (ComD1) through substitution of proteogenic and nonproteogenic amino acids on the hydrophobic binding face of CSP1. The findings from this study not only provided additional structure–activity data that are significant in optimizing CSP1 potency, but also led to the development of potent QS modulators. These CSP‐based QS modulators could be used as privileged scaffolds for the development of antimicrobial agents against pneumococcal infections.

Optimizing CSP1 analogs for modulating quorum sensing inStreptococcus pneumoniaewith bulky, hydrophobic nonproteogenic amino acid substitutions

“…We advanced these results by incorporating multiple mutations containing several of the nonproteogenic amino acids in the CSP1 sequence. 33 The findings from this study provided several important structural insights, specifically the preference of ComD1 for linear, hydrophobic, nonproteogenic amino acids. Combined, the results obtained from these two studies revealed strong potential for even further optimization of the binding interaction between CSP1 and ComD1.…”

“…In the context of S. pneumoniae CSP1, our previous investigations of the CSP1-ComD1 binding interaction revealed that positions 4, 7, 8, 11, and 12 in CSP1 have unoccupied space within the receptor binding site. 32,33 We aimed to assess the steric limit of the CSP1-ComD1 interaction by utilizing bulkier, hydrophobic nonproteogenic substituents. To this end, aliphatic and aromatic hydrophobic residues (Leu, Ile or Phe) in positions 4, 7, 8, 11, and 12 were substituted with the nonproteogenic amino acids, cyclohexylalanine (Cha) or homoleucine (HLeu) (Fig.…”

Mechanistic Studies and In Vivo Efficacy of an Oxadiazole-Containing Antibiotic

“…Excitingly, HSGN-94 showed high efficacy in diminishing the burden of MRSA in a murine skin infection model and also reduced the pro-inflammatory cytokines in MRSA-infected wounds. Antimicrobial resistance is a growing threat, and many groups have disclosed new chemical scaffolds that inhibit bacterial growth. − Detailed mechanistic work to uncover how each of these unique compounds kill bacteria would likely reveal many novel tactics to tackle this global health challenge.…”

Targeting peptide‐based quorum sensing systems for the treatment of gram‐positive bacterial infections

“…Follow‐up studies have focused on optimizing the degree of occupancy of the CSP1 binding pockets within the ComD1 receptor by utilizing conservative substitutions at these key hydrophobic residues of CSP1. [ 92–94 ] Through the incorporation of bulkier, hydrophobic nonproteogenic amino acids, Milly et al were able to develop pneumococcal QS modulators with high potency and superior metabolic stability, while remaining nontoxic against mammalian cells. [ 94 ]…”

“…Follow-up studies have focused on optimizing the degree of occupancy of the CSP1 binding pockets within the ComD1 receptor by utilizing conservative substitutions at these key hydrophobic residues of CSP1. [92][93][94] Through the incorporation of bulkier, hydrophobic nonproteogenic amino acids, Milly et al were able to develop pneumococcal QS modulators with high potency and superior metabolic stability, while remaining nontoxic against mammalian cells. [94] The first position on the pherotype 1 AIP (CSP1, Table 1; with its unique primary structure, each CSP represents a separate pheromone type-pherotype) was found to be necessary for competence development, as Glu1 to Ala mutation (to afford CSP1-E1A) was sufficient to convert the signaling peptide into a competitive inhibitor capable of inhibiting competence induction and regulation of down-stream genes in S. pneumoniae.…”