title: The intramolecular disulfide-stapled structure of laterosporulin, a class IId bacteriocin, conceals a human defensin-like structural module.
abstract: The growing emergence of antibiotic-resistant bacteria has led to the exploration of naturally occurring defense peptides as antimicrobials. In this study, we found that laterosporulin (LS), a class IId bacteriocin, effectively kills active and nonmultiplying cells of both Gram-positive and Gram-negative bacteria. Fluorescence and electron microscopy suggest that growth inhibition occurs because of increased membrane permeability. The crystal structure of LS at 2.0 Å resolution reveals an all-β conformation of this peptide, with four β-strands forming a twisted β-sheet. All six intrinsic cysteines are intramolecularly disulfide-bonded, with two disulfides constraining the N terminus of the peptide and the third disulfide crosslinking the extreme C terminus, resulting in the formation of a closed structure. The significance of disulfides in maintaining the in-solution peptide structure was confirmed by CD and fluorescence analyses. Despite a low overall sequence similarity, LS has disulfide connectivity [C(I)-C(V), C(II)-C(IV), and C(III)-C(VI)] like that of β-defensins and a striking architectural similarity with α-defensins. Therefore LS presents a missing link between bacteriocins and mammalian defensins, and is also a potential antimicrobial lead, in particular against nonmultiplying bacteria.
authors.affiliation: Microbial Type Culture Collection & Gene Bank, CSIR-Institute of Microbial Technology, Chandigarh, India.
authors.forename: Pradip Kumar
authors.initials: PK
authors.lastname: Singh
authors.forename: Vipul
authors.initials: V
authors.lastname: Solanki
authors.forename: Shalley
authors.initials: S
authors.lastname: Sharma
authors.forename: Krishan Gopal
authors.initials: KG
authors.lastname: Thakur
authors.forename: Beena
authors.initials: B
authors.lastname: Krishnan
authors.forename: Suresh
authors.initials: S
authors.lastname: Korpole
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001430:Bacteriocins / Q000737:chemistry* / Q000494:pharmacology; D058675:Brevibacillus / Q000737:chemistry; D002463:Cell Membrane Permeability / Q000187:drug effects; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D023082:Defensins / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry; D024881:Drug Resistance, Bacterial; D006801:Humans; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology; D017433:Protein Structure, Secondary; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D013211:Staphylococcus aureus / Q000187:drug effects
chemical_list: D001430:Bacteriocins; D023082:Defensins; D004220:Disulfides; D010455:Peptides; C000596376:laterosporulin; D003545:Cysteine
keywords: X-ray crystallography; bacteriocin; defensin; microscopy; nonmultiplying cells