Latarcin-1

Cell-penetrating peptides and antimicrobial peptides share physicochemical characteristics and mechanisms of interaction with biological membranes, hence, termed as membrane active peptides. The present study aims at evaluating AMP activity of CPPs. LDP-NLS and LDP are Latarcin 1 derived cell-penetrating peptides and in the current study we have evaluated antifungal and cell-penetrating properties of these CPPs in Fusarium solani. We observed that LDP-NLS and LDP exhibited excellent antifungal activity against the fungus. Cellular uptake experiments with LDP-NLS and LDP showed that LDP-NLS acted as a CPP but LDP uptake into fungal spores and hyphae was negligible. CPP and AMP activity of mutated version of LDP-NLS was also evaluated and it was observed that both the activities of the peptide were compromised, signifying the importance of arginines and lysines present in LDP-NLS for initial interaction of membrane active peptides with biological membranes. Dextrans and Propidium Iodide uptake studies revealed that the mode of entry of LDP-NLS into fungal hyphae is through pore formation. Also, both LDP-NLS and LDP showed no cytotoxicity when infiltered into leaf tissues. Overall, our results suggest that LDP-NLS and LDP are selectively cytotoxic to F. solani and can be a potent peptide based antifungal agents.

Venom peptides anoplin, cupiennin 1a, latarcin 1, latarcin 3a, latarcin 5, melittin, and pandinin 2 are known to have antibacterial properties. In the current study, we examined whether the antimicrobial properties of these venom peptides have any connection to the binding and inhibition of bacterial ATP synthase. Venom peptides inhibited Escherichia coli wild type and mutant membrane-bound F1Fo ATP synthase to varying degrees. Although significant loss of oxidative phosphorylation was observed for wild type, very little loss occurred for null and mutant E. coli strains in the presence of venom peptides. This study also reaffirms that βDELSEED-motif residues of ATP synthase are required for peptide binding. Modified venom peptides with C-terminal amide (NH2) groups caused augmented inhibition of ATP synthase and E. coli cell death. Growth patterns of wild type, null, and mutant strains in the presence of melittin, anoplin, cupiennin 1a, latarcin 1, latarcin 3a, latarcin 5, pandinin 2, and their modified variants suggested the possibility of additional molecular targets. Our results demonstrate that the antimicrobial properties of venom peptides are connected to the binding and inhibition of bacterial ATP synthase. Moreover, selective inhibition of ATP synthase by venom peptides suggests a viable alternative to combat antibiotic-resistant microbial infections.

Cell-penetrating peptides (CPPs) and antimicrobial peptides (AMPs) share certain physicochemical parameters such as amphipathicity, hydrophobicity, cationicity and pI, due to which these two groups of peptides also exhibit overlapping functional characteristics. In our current work, we have evaluated antimicrobial properties of cell-penetrating peptides derived from Latarcin1. Latarcin derived peptide (LDP) exhibited antimicrobial activity against representative microorganisms tested and bactericidal effect against methicillin resistant Staphylococcus aureus (MRSA), which was used as model organism of study in the present work. However, LDP exhibited cytotoxicity against HeLa cells. Further, nuclear localization sequence (NLS) was fused to LDP and interestingly, LDP-NLS showed antimicrobial effect against bacteria, showed bactericidal effect against MRSA and also did not exhibit cytotoxicity in HeLa cells till the highest concentrations tested. Thus, our results inferred that fusion of NLS to LDP significantly reduced cytotoxicity of LDP against HeLa cells (Ponnappan and Chugh, 2017) and exhibited significantly higher cell-penetrating activity in MRSA in comparison to LDP alone. Consolidated results of uptake assays, time-kill assays and PI membrane damage assays show that LDP killed MRSA mainly by membrane damage, where as LDP-NLS might have intracellular targets. Owing to its cell-penetrating activity in HeLa cells and antimicrobial activity against MRSA, LDP-NLS efficiently inhibited intracellular infection of MRSA in HeLa cells as observed in invasion assays. Hence, our results suggest that LDP-NLS is a dual action peptide with AMP and CPP activity and could be potential candidate as peptide antibiotic and drug delivery vector in both mammalian and bacterial cells.