Fig. 4.

S. pneumoniae competence stimulating peptide-1. (A) S. pneumoniae CSP-1 (21) is a quorum sensing peptide that is proposed to form an α-helix in lipid-like environments (pdb 2a1c). (B) Peptide 21 had no structure in water by CD, whereas cyclic analogue (22) formed a well-defined α-helix, shown by CD spectra and (C) NMR structures. (D) Growth curves for S.pneumoniae treated with 10 μM CSP-1 mimetic (22, green), unconstrained analogue (21, red) and PBS control (black) showing at least 10-fold more potent inhibition by 22. Error bars represented ± S.E.M with n≥3.