title: Rattusin structure reveals a novel defensin scaffold formed by intermolecular disulfide exchanges.
abstract: Defensin peptides are essential for innate immunity in humans and other living systems, as they provide protection against infectious pathogens and regulate the immune response. Here, we report the solution structure of rattusin (RTSN), an α-defensin-related peptide, which revealed a novel C2-symmetric disulfide-linked dimeric structure. RTSN was synthesized by solid-phase peptide synthesis (SPPS) and refolded by air oxidation in vitro. Dimerization of the refolded RTSN (r-RTSN) resulted from five intermolecular disulfide (SS) bond exchanges formed by ten cysteines within two protomer chains. The SS bond pairings of r-RTSN were determined by mass analysis of peptide fragments cleaved by trypsin digestion. In addition to mass analysis, nuclear magnetic resonance (NMR) experiments for a C15S mutant and r-RTSN confirmed that the intermolecular SS bond structure of r-RTSN showed an I-V', II-IV', III-III', IV-II', V-I' arrangement. The overall structure of r-RTSN exhibited a cylindrical array, similar to that of β-sandwich folds, with a highly basic surface. Furthermore, fluorescence spectroscopy results suggest that r-RTSN exerts bactericidal activity by damaging membrane integrity. Collectively, these results provide a novel structural scaffold for designing highly potent peptide-based antibiotics suitable for use under various physiological conditions.
authors.affiliation: Department of Chemistry, Chonnam National University, Gwangju 61186, South Korea.|Department of Pharmaceutical Cosmetics, Kwangju Women's University, Gwangju 62396, South Korea.
authors.forename: Hye Jung
authors.initials: HJ
authors.lastname: Min
authors.affiliation: Department of Chemistry, Chonnam National University, Gwangju 61186, South Korea.
authors.forename: Hyosuk
authors.initials: H
authors.lastname: Yun
authors.affiliation: Department of Chemistry, Chonnam National University, Gwangju 61186, South Korea.
authors.forename: Sehyeon
authors.initials: S
authors.lastname: Ji
authors.affiliation: Department of Medical Science, Graduate School and Department of Cellular and Molecular Medicine, School of Medicine, Chosun University, Gwangju 61452, South Korea.
authors.forename: Ganesan
authors.initials: G
authors.lastname: Rajasekaran
authors.affiliation: Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 61005, South Korea.
authors.forename: Jae Il
authors.initials: JI
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Chonnam National University, Gwangju 61186, South Korea.
authors.forename: Jeong-Sun
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Medical Science, Graduate School and Department of Cellular and Molecular Medicine, School of Medicine, Chosun University, Gwangju 61452, South Korea.
authors.forename: Song Yub
authors.initials: SY
authors.lastname: Shin
authors.affiliation: Department of Chemistry, Chonnam National University, Gwangju 61186, South Korea.
authors.forename: Chul Won
authors.initials: CW
authors.lastname: Lee