title: The β-galactosidase (BgaC) of the zoonotic pathogen Streptococcus suis is a surface protein without the involvement of bacterial virulence.
abstract: Streptococcal pathogens have evolved to express exoglycosidases, one of which is BgaC β-galactosidase, to deglycosidate host surface glycolconjucates with exposure of the polysaccharide receptor for bacterial adherence. The paradigm BgaC protein is the bgaC product of Streptococcus, a bacterial surface-exposed β-galactosidase. Here we report the functional definition of the BgaC homologue from an epidemic Chinese strain 05ZYH33 of the zoonotic pathogen Streptococcus suis. Bioinformatics analyses revealed that S. suis BgaC shared the conserved active sites (W240, W243 and Y454). The recombinant BgaC protein of S. suis was purified to homogeneity. Enzymatic assays confirmed its activity of β-galactosidase. Also, the hydrolysis activity was found to be region-specific and sugar-specific for the Gal β-1,3-GlcNAc moiety of oligosaccharides. Flow cytometry analyses combined with immune electron microscopy demonstrated that S. suis BgaC is an atypical surface-anchored protein in that it lacks the "LPXTG" motif for typical surface proteins. Integrative evidence from cell lines and mice-based experiments showed that an inactivation of bgaC does not significantly impair the ability of neither adherence nor anti-phagocytosis, and consequently failed to attenuate bacterial virulence, which is somewhat similar to the scenario seen with S. pneumoniae. Therefore we concluded that S. suis BgaC is an atypical surface-exposed protein without the involvement of bacterial virulence.
authors.affiliation: 1] Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China [2].
authors.forename: Dan
authors.initials: D
authors.lastname: Hu
authors.affiliation: 1] Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China [2].
authors.forename: Fengyu
authors.initials: F
authors.lastname: Zhang
authors.affiliation: University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Huimin
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China.
authors.forename: Lina
authors.initials: L
authors.lastname: Hao
authors.affiliation: Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China.
authors.forename: Xiufang
authors.initials: X
authors.lastname: Gong
authors.affiliation: Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China.
authors.forename: Meiling
authors.initials: M
authors.lastname: Geng
authors.affiliation: Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China.
authors.forename: Min
authors.initials: M
authors.lastname: Cao
authors.affiliation: Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zheng
authors.affiliation: Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China.
authors.forename: Xiuzhen
authors.initials: X
authors.lastname: Pan
authors.affiliation: Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China.
authors.forename: Jiaqi
authors.initials: J
authors.lastname: Tang
authors.affiliation: 1] Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Disease, First Affiliated Hospital, Zhejiang University College of Medicine, Hangzhou, Zhejiang 310003, P. R. China [2] Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, P. R. China.
authors.forename: Youjun
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing 210002, P. R. China.
authors.forename: Changjun
authors.initials: C
authors.lastname: Wang
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D020134:Catalytic Domain; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics*; D051379:Mice; D017434:Protein Structure, Tertiary; D017011:Streptococcus suis / Q000201:enzymology* / Q000254:growth & development / Q000472:pathogenicity; D014774:Virulence / Q000235:genetics; D015047:Zoonoses / Q000382:microbiology*; D001616:beta-Galactosidase / Q000737:chemistry / Q000235:genetics*
chemical_list: D008565:Membrane Proteins; D001616:beta-Galactosidase