Characterization of the antimicrobial activity of the cell-penetrating peptide TAT-RasGAP317-326

Antimicrobial peptides (AMPs) are molecules with antimicrobial activity and could be a promising alternative to classical antibiotics, whose clinical efficiency is undermined by emergence of resistance. Our group is studying one such antibiotic alternative – the antimicrobial peptide TAT-RasGAP317-326. We recently reported the antimicrobial activity of this peptide against a range of Gram-positive and Gram-negative bacteria. In this article, we show that the presence of divalent cations and low pH levels have an impact on TAT-RasGAP317-326 activity, whereas serum proteins only partially reduce the antibacterial activity of TAT-RasGAP317-326. In addition, we show that iron supplementation reduces TAT-RasGAP317-326 binding to bacteria. Using a transcriptomics approach and screening of bacterial mutant libraries, we map the transcriptional response of bacteria when exposed to TAT-RasGAP317-326 and identify cellular pathways that may play a role in bacterial resistance to TAT-RasGAP317-326. We test combinations of TAT-RasGAP317-326 with other AMPs and detect no evidence for an additive effect between any of the peptide combinations. Finally, we perform a resistance selection screen that reveals differences between bacterial strains with respect to their rate of resistance emergence against the TAT-RasGAP317-326 peptide. Taken together, our findings bring a better understanding of how extracellular factors might impact the antimicrobial activity of TAT-RasGAP317-326 peptide and thus contribute basic biology insight into the mechanisms behind TAT-RasGAP317-326 activity, potentially aiding future strategies to improve the efficiency of this peptide in vivo.