Structure-activity correlations for peptaibols obtained from clade Longibrachiatum of : A combined experimental and computational approach.

Integrated disease management and plant protection have been discussed with much fervor in the past decade due to the rising environmental concerns of using industrially produced pesticides. Members of the genus are a subject of considerable research today due to their several properties as biocontrol agents. In our study, the peptaibol production of SZMC 1775, f. SZMC 12546, SZMC 22616, SZMC 22614, SZMC 22606 and SZMC 22611 were investigated to elucidate structure-activity relationships (SARs) between the properties of peptaibols and their 3D structures. The effects of peptaibol mixtures obtained from every strain were examined against nine commonly known bacteria. The lowest minimum inhibitory concentrations (MIC, mg ml) were exerted by f. SZMC 12546 against Gram-positive bacteria, which was also able to inhibit the plant pathogenic Gram-negative . Accelerated molecular dynamics (aMD) simulations were performed in aqueous solvent to explore the folding dynamics of 12 selected peptaibol sequences. The most characteristic difference between the peptaibols from group A and B relies in the 'Gly-Leu-Aib-Pro' and 'Gly-Aib-Aib-Pro' motifs ('Aib' stands for α-aminoisobutyric acid), which imparted a significant effect on the folding dynamics in water and might be correlated with their expressed bioactivity. In our aMD simulation experiments, Group A peptaibols showed more restricted folding dynamics with well-folded helical conformations as the most stable representative structures. This structural stability and dynamics may contribute to their bioactivity against the selected bacterial species.