Hadrurin

A new antimicrobial peptide, hadrurin, was isolated from the venom of the Mexican scorpion Hadrurus aztecus, by gel filtration on a Sephadex G-50 column, followed by high performance liquid chromatography. It is a basic peptide composed of 41 amino-acid residues with a molecular mass of 4436 Da, and contains no cysteines. A model of the three-dimensional folding of hadrurin is compatible with that of an amphipatic molecule with two alpha-helical segments. Hadrurin demonstrates antimicrobial activity at low micromolar concentration, inhibiting the growth of bacteria such as: Salmonella thyphi, Klebsiella pneumoniae, Enterococcus cloacae, Pseudomonas aeruginosa, Escherichia coli and Serratia marscences. It also shows cytolytic activity when tested in human erythrocytes. Hadrurin and two analogs (C-terminal amidated, and all D-enantiomer) were chemically synthesized. They were used to study the possible molecular mechanism of action by testing their ability to dissipate the diffusion potential of liposomes of different compositions. The results obtained indicate that there are no specific receptor molecules for the action of hadrurin, and the most probable mechanism is through a membrane destabilization activity. It is surmised that hadrurin is used by the scorpion as both an attack and defense element against its prey and putative invasive microorganisms. It is a unique peptide among all known antimicrobial peptides described, only partially similar to the N-terminal segment of gaegurin 4 and brevinin 2e, isolated from frog skin. It would certainly be a model molecule for studying new antibiotic activities and peptide-lipid interactions.

Heterometrus xanthopus (Scorpion) is one of the most venomous and ancient arthropods. Its venom contains anti-microbial peptides like hadrurin, scorpine, Pandinin 1, and Pandinin 2 that are able to effectively kill multidrug-resistant pathogens. The present study was conducted to evaluate the anti-bacterial activity of H. xanthopus venom. Six Gram-positive and Gram-negative bacterial strains were tested against 1/100, 1/10, and 1/1 fractions of distilled water diluted and crude venom. 1/100 and 1/10 dilutions were not successful in any of the six bacterial strains studied while the 1/1 dilution was effective on Bacillus subtilis ATCC 6633, Salmonella typhimurium ATCC 14028, and Pseudomonas aeruginosa ATCC 27853 with highest zone of inhibition were obtained on B. subtilis. Crude venom was effective against Enterococcus faecalis ATCC 14506, B. subtilis, S. typhimurium, and P. aeruginosa. The most effective results were observed on B. subtilis.

Background: Microbial antibiotic resistance is a challenging medical problem nowadays. Two scorpion peptides displaying antibiotic activity: hadrurin and vejovine were taken as models for the design of novel shorter peptides with similar activity. Methods: Using the standard Fmoc-based solid phase synthesis technique of Merrifield twelve peptides (18 to 29 amino acids long) were synthesized, purified and assayed against a variety of multi-drug resistant Gram-negative bacteria from clinical isolates. Hemolytic and antiparasitic activities of the peptides and their possible interactions with eukaryotic cells were verified. Release of the fluorophore calcein from liposomes treated with these peptides was measured. Results: A peptide with sequence GILKTIKSIASKVANTVQKLKRKAKNAVA), and three analogs: Δ(Α29), Δ(K12-Q18; Ν26-Α29), and K4N Δ(K12-Q18; Ν26-Α29) were shown to inhibit the growth of Gram-negative (E. coli ATCC25922) and Gram-positive bacteria (S. aureus), as well as multi-drug resistant (MDR) clinical isolated. The antibacterial and antiparasitic activities were found with peptides at 0.78 to 25μM and 5 to 25μM concentration, respectively. These peptides have low cytotoxic and hemolytic activities at concentrations significantly exceeding their minimum inhibitory concentrations (MICs), showing values between 40 and 900μM for their EC50, compared to the parent peptides vejovine and hadrurin that at the same concentration of their MICs lysed more than 50% of human erythrocytes cells. Conclusions: These peptides promise to be good candidates to combat infections caused by Gram-negative bacteria from nosocomial infections. General significance: Our results confirm that well designed synthetic peptides can be an alternative for solving the lack of effective antibiotics to control bacterial infections.