title: Crystal Structure of a Soluble Fragment of the Membrane Fusion Protein HlyD in a Type I Secretion System of Gram-Negative Bacteria.
abstract: The protein toxin HlyA of Escherichia coli is exported without a periplasmic intermediate by the type I secretion system (T1SS). The T1SS is composed of an inner membrane ABC transporter HlyB, an outer-membrane channel protein TolC, and a membrane fusion protein HlyD. However, the assembly of the T1SS remains to be elucidated. In this study, we determine the crystal structure of a part of the C-terminal periplasmic domain of HlyD. The long α-helical domain consisting of three α helices and a lipoyl domain was identified in the crystal structure. Based on the HlyD structure, we modeled the hexameric assembly of HlyD with a long α-helical barrel, which formed a complex with TolC in an intermeshing cogwheel-to-cogwheel manner, as observed in tripartite RND-type drug efflux pumps. These observations provide a structural blueprint for understanding the type I secretion system in pathogenic Gram-negative bacteria.
authors.affiliation: Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Room #200-1041, 1 Gwanak-ro, Gwanak-gu, Seoul 151-921, Republic of Korea.
authors.forename: Jin-Sik
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Room #200-1041, 1 Gwanak-ro, Gwanak-gu, Seoul 151-921, Republic of Korea.
authors.forename: Saemee
authors.initials: S
authors.lastname: Song
authors.affiliation: Department of Life Science, Chung-Ang University, Seoul, 156-756 Republic of Korea.
authors.forename: Minho
authors.initials: M
authors.lastname: Lee
authors.affiliation: Department of Life Science, Chung-Ang University, Seoul, 156-756 Republic of Korea.
authors.forename: Seunghwa
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Life Science, Chung-Ang University, Seoul, 156-756 Republic of Korea.
authors.forename: Kangseok
authors.initials: K
authors.lastname: Lee
authors.affiliation: Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Room #200-1041, 1 Gwanak-ro, Gwanak-gu, Seoul 151-921, Republic of Korea. Electronic address: hanc210@snu.ac.kr.
authors.forename: Nam-Chul
authors.initials: NC
authors.lastname: Ha
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D000072417:Protein Domains; D017433:Protein Structure, Secondary; D000069177:Type I Secretion Systems / Q000737:chemistry / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C065231:HlyD protein, E coli; D026901:Membrane Transport Proteins; D000069177:Type I Secretion Systems; C073126:tolC protein, E coli