title: Functional analysis of the CpsA protein of Streptococcus agalactiae.
abstract: Streptococcal pathogens, such as the group B streptococcus (GBS) Streptococcus agalactiae, are an important cause of systemic disease, which is facilitated in part by the presence of a polysaccharide capsule. The CpsA protein is a putative transcriptional regulator of the capsule locus, but its exact contribution to regulation is unknown. To address the role of CpsA in regulation, full-length GBS CpsA and two truncated forms of the protein were purified and analyzed for DNA-binding ability. Assays demonstrated that CpsA is able to bind specifically to two putative promoters within the capsule operon with similar affinity, and full-length protein is required for specificity. Functional characterization of CpsA confirmed that the ΔcpsA strain produced less capsule than did the wild type and demonstrated that the production of full-length CpsA or the DNA-binding region of CpsA resulted in increased capsule levels. In contrast, the production of a truncated form of CpsA lacking the extracellular LytR domain (CpsA-245) in the wild-type background resulted in a dominant-negative decrease in capsule production. GBS expressing CpsA-245, but not the ΔcpsA strain, was attenuated in human whole blood. However, the ΔcpsA strain showed significant attenuation in a zebrafish infection model. Furthermore, chain length was observed to be variable in a CpsA-dependent manner, but could be restored to wild-type levels when grown with lysozyme. Taken together, these results suggest that CpsA is a modular protein influencing multiple regulatory functions that may include not only capsule synthesis but also cell wall associated factors.
authors.affiliation: Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, MI, USA.
authors.forename: Brett R
authors.initials: BR
authors.lastname: Hanson
authors.forename: Donna L
authors.initials: DL
authors.lastname: Runft
authors.forename: Cale
authors.initials: C
authors.lastname: Streeter
authors.forename: Abhin
authors.initials: A
authors.lastname: Kumar
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Carion
authors.forename: Melody N
authors.initials: MN
authors.lastname: Neely
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000096:biosynthesis; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004912:Erythrocytes / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013290:Streptococcal Infections / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D014774:Virulence; D015027:Zebrafish
chemical_list: D001426:Bacterial Proteins