title: Structures of human host defense cathelicidin LL-37 and its smallest antimicrobial peptide KR-12 in lipid micelles.
abstract: As a key component of the innate immunity system, human cathelicidin LL-37 plays an essential role in protecting humans against infectious diseases. To elucidate the structural basis for its targeting bacterial membrane, we have determined the high quality structure of (13)C,(15)N-labeled LL-37 by three-dimensional triple-resonance NMR spectroscopy, because two-dimensional (1)H NMR did not provide sufficient spectral resolution. The structure of LL-37 in SDS micelles is composed of a curved amphipathic helix-bend-helix motif spanning residues 2-31 followed by a disordered C-terminal tail. The helical bend is located between residues Gly-14 and Glu-16. Similar chemical shifts and (15)N nuclear Overhauser effect (NOE) patterns of the peptide in complex with dioctanoylphosphatidylglycerol (D8PG) micelles indicate a similar structure. The aromatic rings of Phe-5, Phe-6, Phe-17, and Phe-27 of LL-37, as well as arginines, showed intermolecular NOE cross-peaks with D8PG, providing direct evidence for the association of the entire amphipathic helix with anionic lipid micelles. The structure of LL-37 serves as a model for understanding the structure and function relationship of homologous primate cathelicidins. Using synthetic peptides, we also identified the smallest antibacterial peptide KR-12 corresponding to residues 18-29 of LL-37. Importantly, KR-12 displayed a selective toxic effect on bacteria but not human cells. NMR structural analysis revealed a short three-turn amphipathic helix rich in positively charged side chains, allowing for effective competition for anionic phosphatidylglycerols in bacterial membranes. KR-12 may be a useful peptide template for developing novel antimicrobial agents of therapeutic use.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA. gwang@unmc.edu
authors.forename: Guangshun
authors.initials: G
authors.lastname: Wang
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000494:pharmacology* / Q000502:physiology; D001419:Bacteria / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D054804:Cathelicidins / Q000737:chemistry*; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008823:Micelles; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D010649:Phenylalanine / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry
chemical_list: D023181:Antimicrobial Cationic Peptides; D001426:Bacterial Proteins; D054804:Cathelicidins; D008055:Lipids; D008823:Micelles; D010446:Peptide Fragments; D010715:Phosphatidylglycerols; C534394:cathelicidin LL-37 (18-29), human; D012967:Sodium Dodecyl Sulfate; D010649:Phenylalanine