title: Structural and functional characterization of the conserved salt bridge in mammalian paneth cell alpha-defensins: solution structures of mouse CRYPTDIN-4 and (E15D)-CRYPTDIN-4.
abstract: alpha-Defensins are mediators of mammalian innate immunity, and knowledge of their structure-function relationships is essential for understanding their mechanisms of action. We report here the NMR solution structures of the mouse Paneth cell alpha-defensin cryptdin-4 (Crp4) and a mutant (E15D)-Crp4 peptide, in which a conserved Glu(15) residue was replaced by Asp. Structural analysis of the two peptides confirms the involvement of this Glu in a conserved salt bridge that is removed in the mutant because of the shortened side chain. Despite disruption of this structural feature, the peptide variant retains a well defined native fold because of a rearrangement of side chains, which result in compensating favorable interactions. Furthermore, salt bridge-deficient Crp4 mutants were tested for bactericidal effects and resistance to proteolytic degradation, and all of the variants had similar bactericidal activities and stability to proteolysis. These findings support the conclusion that the function of the conserved salt bridge in Crp4 is not linked to bactericidal activity or proteolytic stability of the mature peptide.
authors.affiliation: Department of Chemistry and Biomedical Sciences, University of Kalmar, SE-391 82 Kalmar, Sweden. johan.rosengren@hik.se
authors.forename: K Johan
authors.initials: KJ
authors.lastname: Rosengren
authors.forename: Norelle L
authors.initials: NL
authors.lastname: Daly
authors.forename: Liselotte M
authors.initials: LM
authors.lastname: Fornander
authors.forename: Linda M H
authors.initials: LM
authors.lastname: Jönsson
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Shirafuji
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Qu
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Vogel
authors.forename: Andre J
authors.initials: AJ
authors.lastname: Ouellette
authors.forename: David J
authors.initials: DJ
authors.lastname: Craik
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D020783:Matrix Metalloproteinase 7 / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011817:Rabbits; D012996:Solutions; D013329:Structure-Activity Relationship; D013696:Temperature; D023084:alpha-Defensins / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D012996:Solutions; D023084:alpha-Defensins; C401847:cryptdin 4, mouse; D020783:Matrix Metalloproteinase 7