title: Modification of the CpsA protein reveals a role in alteration of the Streptococcus agalactiae cell envelope.
abstract: The bacterial cell envelope is a crucial first line of defense for a systemic pathogen, with production of capsular polysaccharides and maintenance of the peptidoglycan cell wall serving essential roles in survival in the host environment. The LytR-CpsA-Psr proteins are important for cell envelope maintenance in many Gram-positive species. In this study, we examined the role of the extracellular domain of the CpsA protein of the zoonotic pathogen group B Streptococcus in capsule production and cell wall integrity. CpsA has multiple functional domains, including a DNA-binding/transcriptional activation domain and a large extracellular domain. We demonstrated that episomal expression of extracellularly truncated CpsA causes a dominant-negative effect on capsule production when expressed in the wild-type strain. Regions of the extracellular domain essential to this phenotype were identified. The dominant-negative effect could be recapitulated by addition of purified CpsA protein or a short CpsA peptide to cultures of wild-type bacteria. Changes in cell wall morphology were also observed when the dominant-negative peptide was added to wild-type cultures. Fluorescently labeled CpsA peptide could be visualized bound at the mid-cell region near the division septae, suggesting a novel role for CpsA in cell division. Finally, expression of truncated CpsA also led to attenuation of virulence in zebrafish models of infection, to levels below that of a cpsA deletion strain, demonstrating the key role of the extracellular domain in virulence of GBS.
authors: Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, Michigan, USA.
authors: Hannah M
authors: HM
authors: Rowe
authors: Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, Michigan, USA.
authors: Brett R
authors: BR
authors: Hanson
authors: Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, Michigan, USA.
authors: Donna L
authors: DL
authors: Runft
authors: Eugene Applebaum College of Pharmacy, Wayne State University, Detroit, Michigan, USA.
authors: Qian
authors: Q
authors: Lin
authors: Eugene Applebaum College of Pharmacy, Wayne State University, Detroit, Michigan, USA.
authors: Steve M
authors: SM
authors: Firestine
authors: Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, Michigan, USA mneely@med.wayne.edu.
authors: Melody N
authors: MN
authors: Neely
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics*; D002455:Cell Division / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall; D004268:DNA-Binding Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics*; D010957:Plasmids / Q000235:genetics; D017434:Protein Structure, Tertiary; D013290:Streptococcal Infections; D013292:Streptococcus agalactiae / Q000166:cytology / Q000235:genetics / Q000472:pathogenicity*; D015027:Zebrafish / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D008565:Membrane Proteins
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