Supplementary Material for: The Central Kink Region of Fowlicidin-2, an α-Helical Host Defense Peptide, Is Critically Involved in Bacterial Killing and Endotoxin Neutralization Xiao Y. Herrera A.I. Bommineni Y.R. Soulages J.L. Prakash O. Zhang G. 10.6084/m9.figshare.5120527.v1 https://karger.figshare.com/articles/dataset/Supplementary_Material_for_The_Central_Kink_Region_of_Fowlicidin-2_an_-Helical_Host_Defense_Peptide_Is_Critically_Involved_in_Bacterial_Killing_and_Endotoxin_Neutralization/5120527 Fowlicidins are a group of newly identified chicken cathelicidin host defense peptides. We have shown that the putatively mature fowlicidin-2 of 31 amino acid residues possesses potent antibacterial and lipopolysaccharide (LPS)- neutralizing activities, but with a noticeable toxicity to mammalian cells. As a first step in exploring the structure-activity relationships of fowlicidin-2, in this study we determined its tertiary structure by nuclear magnetic resonance spectroscopy. Unlike the majority of cathelicidins, which are composed of a predominant α-helix with a short hinge sequence near the center, fowlicidin-2 consists of 2 well-defined α-helical segments (residues 6–12 and 23–27) connected by a long extensive kink (residues 13–20) induced by proline. To further investigate the functional significance of each of these structural components, several N- and C-terminal deletion analogs of fowlicidin-2 were synthesized and analyzed for their antibacterial, cytotoxic and LPS-neutralizing activities. Our results indicated that neither the N- nor C-terminal α-helix alone is sufficient to confer any function. Rather, fowlicidin-2(1–18) and fowlicidin-2(15–31), 2 α-helical segments with inclusion of the central cationic kink region, retained substantial capacities to kill bacteria and neutralize the LPS-induced proinflammatory response, relative to the parent peptide. More desirably, these 2 peptide analogs showed substantially reduced toxicity to human erythrocytes and epithelial cells, indicative of improved potential as antibacterial and antisepsis agents. To our knowledge, fowlicidin-2 is the first α-helical cathelicidin, with the central kink region shown to be critically important in killing bacteria and neutralizing LPS. 2008-11-14 00:00:00 Host defense peptide Antimicrobial peptides Cathelicidins Innate immunity Structure-activity relationship Endotoxin Antibiotic resistance