Bis‐(3′,5′)‐cyclic dimeric guanosine monophosphate, c‐di‐GMP, is an important signaling molecule in bacteria. It is involved, for example, in the regulation of biofilm formation, cell cycle progression, and virulence of several pathogens. Since c-di-GMP has only been observed in bacteria and simple eukaryotes but not in higherâ€order organisms, it is an attractive target for the fight against bacterial infections.
The development of selective binders of c-di-GMP is difficult and consequently most efforts towards therapeutically active compounds have focused on interfering with protein regulators of c-di-GMP rather than targeting the messenger molecule itself. Aside from natural c-di-GMP binding proteins and aptamers, only small intercalating molecules are known to bind c-di-GMP. Scientists in the Wennemers Group envisioned shortâ€chain peptides as attractive alternatives for binding c-di-GMP since they are biocompatible and their structural and functional properties are tunable to fit the needs of the specific target molecule.
In work published in Angewandte Chemie, group members present functionalized proline-rich peptides that bind c-di-GMP in aqueous solution. They also show that the functionalized tetrapeptides, which were identified through combinatorial screening, inhibit biofilm growth in P. aeruginosa.
In summary, we have shown that short prolineâ€rich peptides bearing cationic and aromatic groups bind the bacterial second messenger c-di-GMP selectivity over closely related nucleotides with binding affinities in the micromolar range. In addition, the peptides were found to inhibit the formation of biofilms by the opportunistic pathogen P. aeruginosa.
Spectroscopic, molecular modeling, and SAR studies revealed that the binding is driven by a combination of π–π stacking, H-bonding, and electrostatic interactions between the peptide and c-di-GMP.
These are the first examples of short peptides that bind c-di-GMP selectively and result in a phenotypic response in bacteria, and the results open intriguing perspectives for the development of functionalized c-di-GMP binding peptides. Such compounds might not only be useful for therapeutic applications, for example, as an aerosol formulation for patients suffering from lung infections, but also for imaging studies, thereby providing an entry point into the quantitative analysis of smallâ€molecule signaling networks in-vitro and in-vivo.
Functionalized Proline-Rich Peptides Bind the Bacterial Second Messenger c-di-GMP
Carlotta Foletti, Rolf A. Kramer, Harald Mauser, Urs Jenal, Konrad H. Bleicher, and Helma Wennemers
Angew. Chemie, Intl. Ed., Volume 57, Issue 21, May 22, 2018, Pages 6150-6154