Alteration of the mode of antibacterial action of a defensin by the amino-terminal loop substitution.

摘要: Ancient invertebrate-type and classical insect-type defensins (AITDs CITDs) are two groups of evolutionarily related antimicrobial peptides (AMPs) that adopt a conserved cysteine-stabilized α-helical β-sheet (CSαβ) fold with different amino-terminal loop (n-loop) size diverse modes antibacterial action. Although they both identified as inhibitors cell wall biosynthesis, only CITDs evolved membrane disruptive ability by peptide oligomerization to form pores. To understand how this occurred, we modified micasin, fungus-derived AITDs non-membrane mechanism, substituting its n-loop an insect-derived CITDs. After air oxidization, the synthetic hybrid defensin (termed Al-M) was structurally circular dichroism (CD) functionally evaluated permeability assays electronic microscopic observation. Results showed Al-M folded into native-like structure, determined CD spectrum is similar micasin. highly efficacious against Gram-positive bacterium Bacillus megaterium lethal concentration 1.76μM. As expected, in contrast killed bacteria through mechanism The alteration action supports key role extension assembling functional surface for disruption. Our work provides mechanical evidence evolutionary relationship between