title: Single-point mutation-mediated local amphipathic adjustment dramatically enhances antibacterial activity of a fungal defensin.
abstract: The emergence and rapid spread of multiresistant bacteria has lead to an urgent need for novel antimicrobials. Based on single-point substitutions, we generated a series of mutants of micasin, a dermatophytic defensin, with enhanced activities against multiple clinical isolates of Staphylococcus species, including 4 antibiotic-resistant strains. We first mapped the functional surface of micasin by alanine-scanning mutational analysis of its highly exposed residues, through which we found that substitution of site 8 (acidic Glu) dramatically enhanced bacterial killing of this peptide. Structural analysis indicates that this single point mutation could result in a functional local amphipathic architecture. Four different types of side chains (hydrophobic, cationic polar, neutral polar, and acidic polar) were introduced at site 8 to clarify the role of this local architecture in micasin function. The results show that all mutants displayed increased antibacterial activity with the exception of the acidic replacement. These mutants with enhanced activity exhibited low hemolysis and cytotoxicity and showed high serum stability, indicating their therapeutic potential. Our work represents the first example of structural fine-tuning to largely improve the antibacterial potency of a dermatophytic defensin.-Wu, J., Gao, B., Zhu, S. Single-point mutation-mediated local amphipathic adjustment dramatically enhances antibacterial activity of a fungal defensin.
authors.affiliation: Group of Peptide Biology and Evolution, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jiajia
authors.initials: J
authors.lastname: Wu
authors.affiliation: Group of Peptide Biology and Evolution, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Gao
authors.affiliation: Group of Peptide Biology and Evolution, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China zhusy@ioz.ac.cn.
authors.forename: Shunyi
authors.initials: S
authors.lastname: Zhu
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects*; D023082:Defensins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology; D008864:Microsporum / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D017354:Point Mutation; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D023082:Defensins; D010455:Peptides; C574456:micasin
keywords: MRSA; micasin; peptide structure