title: Structure-function studies of chemokine-derived carboxy-terminal antimicrobial peptides.
abstract: Recent reports which show that several chemokines can act as direct microbicidal agents have drawn renewed attention to these chemotactic signalling proteins. Here we present a structure-function analysis of peptides derived from the human chemokines macrophage inflammatory protein-3alpha (MIP-3alpha/CCL20), interleukin-8 (IL-8), neutrophil activating protein-2 (NAP-2) and thrombocidin-1 (TC-1). These peptides encompass the C-terminal alpha-helices of these chemokines, which have been suggested to be important for the direct antimicrobial activities. Far-UV CD spectroscopy showed that the peptides are unstructured in aqueous solution and that a membrane mimetic solvent is required to induce a helical secondary structure. A co-solvent mixture was used to determine solution structures of the peptides by two-dimensional (1)H-NMR spectroscopy. The highly cationic peptide, MIP-3alpha(51-70), had the most pronounced antimicrobial activity and displayed an amphipathic structure. A shorter version of this peptide, MIP-3alpha(59-70), remained antimicrobial but its structure and mechanism of action were unlike that of the former peptide. The NAP-2 and TC-1 proteins differ in their sequences only by the deletion of two C-terminal residues in TC-1, but intact TC-1 is a very potent antimicrobial while NAP-2 is inactive. The corresponding C-terminal peptides, NAP-2(50-70) and TC-1(50-68), had very limited and no bactericidal activity, respectively. This suggests that other regions of TC-1 contribute to its bactericidal activity. Altogether, this work provides a rational structural basis for the biological activities of these peptides and proteins and highlights the importance of experimental characterization of peptide fragments as distinct entities because their activities and structural properties may differ substantially from their parent proteins.
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
authors.forename: Leonard T
authors.initials: LT
authors.lastname: Nguyen
authors.forename: David I
authors.initials: DI
authors.lastname: Chan
authors.forename: Laura
authors.initials: L
authors.lastname: Boszhard
authors.forename: Sebastian A J
authors.initials: SA
authors.lastname: Zaat
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Vogel
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology; D001412:Bacillus subtilis / Q000254:growth & development; D018925:Chemokines / Q000737:chemistry* / Q000494:pharmacology; D004926:Escherichia coli / Q000254:growth & development; D006801:Humans; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology; D017433:Protein Structure, Secondary; D013211:Staphylococcus aureus / Q000254:growth & development; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D018925:Chemokines; D010455:Peptides