title: Structural, Functional, and Immunogenic Insights on Cu,Zn Superoxide Dismutase Pathogenic Virulence Factors from Neisseria meningitidis and Brucella abortus.
abstract: Bacterial pathogens Neisseria meningitidis and Brucella abortus pose threats to human and animal health worldwide, causing meningococcal disease and brucellosis, respectively. Mortality from acute N. meningitidis infections remains high despite antibiotics, and brucellosis presents alimentary and health consequences. Superoxide dismutases are master regulators of reactive oxygen and general pathogenicity factors and are therefore therapeutic targets. Cu,Zn superoxide dismutases (SODs) localized to the periplasm promote survival by detoxifying superoxide radicals generated by major host antimicrobial immune responses. We discovered that passive immunization with an antibody directed at N. meningitidis SOD (NmSOD) was protective in a mouse infection model. To define the relevant atomic details and solution assembly states of this important virulence factor, we report high-resolution and X-ray scattering analyses of NmSOD and of SOD from B. abortus (BaSOD). The NmSOD structures revealed an auxiliary tetrahedral Cu-binding site bridging the dimer interface; mutational analyses suggested that this metal site contributes to protein stability, with implications for bacterial defense mechanisms. Biochemical and structural analyses informed us about electrostatic substrate guidance, dimer assembly, and an exposed C-terminal epitope in the NmSOD dimer. In contrast, the monomeric BaSOD structure provided insights for extending immunogenic peptide epitopes derived from the protein. These collective results reveal unique contributions of SOD to pathogenic virulence, refine predictive motifs for distinguishing SOD classes, and suggest general targets for antibacterial immune responses. The identified functional contributions, motifs, and targets distinguishing bacterial and eukaryotic SOD assemblies presented here provide a foundation for efforts to develop SOD-specific inhibitors of or vaccines against these harmful pathogens.
  
  
  OBJECTIVE
  By protecting microbes against reactive oxygen insults, SODs aid survival of many bacteria within their hosts. Despite the ubiquity and conservation of these key enzymes, notable species-specific differences relevant to pathogenesis remain undefined. To probe mechanisms that govern the functioning of Neisseria meningitidis and Brucella abortus SODs, we used X-ray structures, enzymology, modeling, and murine infection experiments. We identified virulence determinants common to the two homologs, assembly differences, and a unique metal reservoir within meningococcal SOD that stabilizes the enzyme and may provide a safeguard against copper toxicity. The insights reported here provide a rationale and a basis for SOD-specific drug design and an extension of immunogen design to target two important pathogens that continue to pose global health threats.
authors.affiliation: Department of Integrative Structural and Computational Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, USA Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
authors.forename: Ashley J
authors.initials: AJ
authors.lastname: Pratt
authors.affiliation: Department of Integrative Structural and Computational Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: DiDonato
authors.affiliation: Department of Integrative Structural and Computational Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, USA Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Shin
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, New York, USA.
authors.forename: Diane E
authors.initials: DE
authors.lastname: Cabelli
authors.affiliation: Department of Integrative Structural and Computational Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, USA.
authors.forename: Cami K
authors.initials: CK
authors.lastname: Bruns
authors.affiliation: National Animal Disease Center, Ruminant Diseases and Immunology, Ames, Iowa, USA.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Belzer
authors.affiliation: Public Health England, Porton Down, Salisbury, United Kingdom.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Gorringe
authors.affiliation: Section of Paediatrics, Department of Medicine, Imperial College London, St. Mary's Campus, London, England, United Kingdom.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Langford
authors.affiliation: National Animal Disease Center, Ruminant Diseases and Immunology, Ames, Iowa, USA.
authors.forename: Louisa B
authors.initials: LB
authors.lastname: Tabatabai
authors.affiliation: Section of Paediatrics, Department of Medicine, Imperial College London, St. Mary's Campus, London, England, United Kingdom.
authors.forename: J Simon
authors.initials: JS
authors.lastname: Kroll
authors.affiliation: Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Tainer
authors.affiliation: Department of Integrative Structural and Computational Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, USA edg@scripps.edu.
authors.forename: Elizabeth D
authors.initials: ED
authors.lastname: Getzoff
mesh_terms: D000818:Animals; D000906:Antibodies / Q000008:administration & dosage / Q000276:immunology; D000936:Antigen-Antibody Complex / Q000648:ultrastructure*; D001666:Binding Sites, Antibody; D002004:Brucella Vaccine / Q000276:immunology; D002003:Brucella abortus / Q000276:immunology* / Q000472:pathogenicity; D002006:Brucellosis / Q000276:immunology / Q000517:prevention & control; D018360:Crystallography, X-Ray; D004195:Disease Models, Animal; D007116:Immunization, Passive / Q000379:methods; D008585:Meningitis, Meningococcal / Q000276:immunology / Q000517:prevention & control; D022401:Meningococcal Vaccines / Q000276:immunology; D051379:Mice; D009345:Neisseria meningitidis / Q000276:immunology* / Q000472:pathogenicity; D013482:Superoxide Dismutase / Q000235:genetics / Q000276:immunology* / Q000648:ultrastructure*; D037521:Virulence Factors / Q000276:immunology
chemical_list: D000906:Antibodies; D000936:Antigen-Antibody Complex; D002004:Brucella Vaccine; D022401:Meningococcal Vaccines; D037521:Virulence Factors; D013482:Superoxide Dismutase