title: Crystal structure of the ADP-ribosylating component of BEC, the binary enterotoxin of Clostridium perfringens.
abstract: Binary enterotoxin of Clostridium perfringens (BEC), consisting of the components BECa and BECb, was recently identified as a novel enterotoxin produced by C. perfringens that causes acute gastroenteritis in humans. Although the detailed mechanism of cell intoxication by BEC remains to be defined, BECa shows both NAD+-glycohydrolase and actin ADP-ribosyltransferase activities in the presence of NAD+. In this study, we determined the first crystal structure of BECa in its apo-state and in complex with NADH. The structure of BECa shows striking resemblance with other binary actin ADP-ribosylating toxins (ADPRTs), especially in terms of its overall protein fold and mechanisms of substrate recognition. We present a detailed picture of interactions between BECa and NADH, including bound water molecules located near the C1'-N glycosidic bond of NADH and the catalytically important ADP-ribosylating turn-turn (ARTT) loop. We observed that the conformational rearrangement of the ARTT loop, possibly triggered by a conformational change involving a conserved tyrosine residue coupled with substrate binding, plays a crucial role in catalysis by properly positioning a catalytic glutamate residue in the E-X-E motif of the ARTT loop in contact with the nucleophile. Our results for BECa provide insight into the common catalytic mechanism of the family of binary actin ADPRTs.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Kawahara
authors.affiliation: Osaka Prefectural Institute of Public Health, Osaka, Osaka, Japan; Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Yonogi
authors.affiliation: Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Munetomo
authors.affiliation: Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan.
authors.forename: Hiroya
authors.initials: H
authors.lastname: Oki
authors.affiliation: Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Yoshida
authors.affiliation: Osaka Prefectural Institute of Public Health, Osaka, Osaka, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kumeda
authors.affiliation: Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan.
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Matsuda
authors.affiliation: Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Kodama
authors.affiliation: Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan.
authors.forename: Tadayasu
authors.initials: T
authors.lastname: Ohkubo
authors.affiliation: Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Iida
authors.affiliation: Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan. Electronic address: nshota@gen-info.osaka-u.ac.jp.
authors.forename: Shota
authors.initials: S
authors.lastname: Nakamura
mesh_terms: D000199:Actins / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000378:metabolism; D018360:Crystallography, X-Ray; D004768:Enterotoxins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation
chemical_list: D000199:Actins; C000620297:BECa protein, Clostridium perfringens; C000620298:BECb protein, Clostridium perfringens; D004768:Enterotoxins; D009243:NAD; D000244:Adenosine Diphosphate
keywords: Binary enterotoxin; C. perfringens; Protein structure; X-ray crystallography