title: The 1.59Å resolution structure of the minor pseudopilin EpsH of Vibrio cholerae reveals a long flexible loop.
abstract: The type II secretion complex exports folded proteins from the periplasm to the extracellular milieu. It is used by the pathogenic bacterium Vibrio cholerae to export several proteins, including its major virulence factor, cholera toxin. The pseudopilus is an essential component of the type II secretion system and likely acts as a piston to push the folded proteins across the outer membrane through the secretin pore. The pseudopilus is composed of the major pseudopilin, EpsG, and four minor pseudopilins, EpsH, EpsI, EpsJ and EpsK. We determined the x-ray crystal structure of the head domain of EpsH at 1.59Å resolution using molecular replacement with the previously reported EpsH structure, 2qv8, as the template. Three additional N-terminal amino acids present in our construct prevent an artifactual conformation of residues 160-166, present in one of the two monomers of the 2qv8 structure. Additional crystal contacts stabilize a long flexible loop comprised of residues 104-135 that is more disordered in the 2qv8 structure but is partially observed in our structure in very different positions for the two EpsH monomers in the asymmetric unit. In one of the conformations the loop is highly extended. Modeling suggests the highly charged loop is capable of contacting EpsG and possibly secreted protein substrates, suggesting a role in specificity of pseudopilus assembly or secretion function.
authors: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; Center for Microbial Pathogenesis, Michigan State University, East Lansing, MI 48824, USA.
authors: Kannan
authors: K
authors: Raghunathan
authors: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; Center for Microbial Pathogenesis, Michigan State University, East Lansing, MI 48824, USA.
authors: Frank S
authors: FS
authors: Vago
authors: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; Center for Microbial Pathogenesis, Michigan State University, East Lansing, MI 48824, USA.
authors: David
authors: D
authors: Grindem
authors: Center for Microbial Pathogenesis, Michigan State University, East Lansing, MI 48824, USA; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
authors: Terry
authors: T
authors: Ball
authors: Center for Microbial Pathogenesis, Michigan State University, East Lansing, MI 48824, USA; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA; Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA.
authors: William J
authors: WJ
authors: Wedemeyer
authors: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; Center for Microbial Pathogenesis, Michigan State University, East Lansing, MI 48824, USA.
authors: Michael
authors: M
authors: Bagdasarian
authors: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; Center for Microbial Pathogenesis, Michigan State University, East Lansing, MI 48824, USA. Electronic address: arvidso4@msu.edu.
authors: Dennis N
authors: DN
authors: Arvidson
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D036781:Fimbriae Proteins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014734:Vibrio cholerae / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins
keywords: EpsH; GspH; Pseudopilin; Pseudopilus; Type II secretion; Vibrio cholerae