title: Functional analysis of Streptococcus pyogenes nuclease A (SpnA), a novel group A streptococcal virulence factor.
abstract: Streptococcus pyogenes nuclease A (SpnA) is a recently discovered DNase that plays a role in virulence as shown in a mouse infection model. SpnA is the only cell wall-anchored DNase found in S. pyogenes thus far and shows a unique protein architecture. The C-terminal nuclease domain contains highly conserved catalytic site and Mg(2+) binding site residues. However, expression of the SpnA nuclease domain alone resulted in a soluble, but enzymatically inactive protein. We found that at least two out of three oligonucleotide/oligosaccharide-binding fold motifs found in the N-terminal domain are required for SpnA activity, probably contributing to substrate binding. Using a combination of a spnA deletion mutant and a Lactococcus lactis'gain-of-function' mutant, we have shown that SpnA promotes survival in whole human blood and in neutrophil killing assays and this is, at least in part, achieved by the destruction of neutrophil extracellular traps (NETs). We observed higher frequencies for anti-SpnA antibodies in streptococcal disease patient sera (79%, n = 19) compared with sera from healthy donors (33%, n = 9) suggesting that SpnA is expressed during infection. Detection of anti-SpnA antibodies in patient serum might be useful for the diagnostic of post-streptococcal diseases, such as acute rheumatic fever or glomerulonephritis.
authors.affiliation: Department of Molecular Medicine & Pathology, School of Medical Sciences, University of Auckland, Auckland, New Zealand.
authors.forename: Ann
authors.initials: A
authors.lastname: Chang
authors.forename: Adrina
authors.initials: A
authors.lastname: Khemlani
authors.forename: HaeJoo
authors.initials: H
authors.lastname: Kang
authors.forename: Thomas
authors.initials: T
authors.lastname: Proft
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D001665:Binding Sites; D003851:Deoxyribonucleases / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D017434:Protein Structure, Tertiary; D013290:Streptococcal Infections / Q000276:immunology / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000276:immunology; D037521:Virulence Factors / Q000737:chemistry / Q000235:genetics / Q000276:immunology*
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors; D003851:Deoxyribonucleases; C029970:nuclease alpha