title: SpyA is a membrane-bound ADP-ribosyltransferase of Streptococcus pyogenes which modifies a streptococcal peptide, SpyB.
abstract: All sequenced genomes of Streptococcus pyogenes (Group A Streptococcus, GAS) encode a protein, SpyA, with homology to C3-like ADP-ribosyltransferase toxins. SpyA is a novel virulence factor which plays a role in pathogenesis in a mouse model of soft-tissue infection. In this study we demonstrate that SpyA is a surface-exposed membrane protein which is anchored to the streptococcal membrane by an N-terminal transmembrane sequence. We identified a small gene upstream of spyA, designated spyB, which encodes a peptide of 35 amino acids, and is co-transcribed with spyA. Expression of spyBA is strongly influenced by translational coupling: mutational inactivation of spyB translation completely abolishes translation of spyA. spyB expression increases with increasing cell density and reaches its maximum at late exponential growth phase. The SpyB N-terminus is predicted to fold into an amphipathic α-helix, a structural motif that targets a protein to the cytoplasmic membrane. Consistent with the prediction, we found that a SpyB fusion with peptide affinity tags is located in the streptococcal membrane. An ADP-ribosylation assay with recombinant SpyA demonstrated that SpyA modifies SpyB. Thus, our study suggests that ADP-ribosylation of SpyB may be an important function of SpyA.
authors.affiliation: Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536-0509, USA. nkorotkova@uky.edu
authors.forename: Natalia
authors.initials: N
authors.lastname: Korotkova
authors.forename: Jessica S
authors.initials: JS
authors.lastname: Hoff
authors.forename: Devon M
authors.initials: DM
authors.lastname: Becker
authors.forename: John Kyle Heggen
authors.initials: JK
authors.lastname: Quinn
authors.forename: Laura M
authors.initials: LM
authors.lastname: Icenogle
authors.forename: Steve L
authors.initials: SL
authors.lastname: Moseley
mesh_terms: D036002:ADP Ribose Transferases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009876:Operon; D010957:Plasmids; D017433:Protein Structure, Secondary; D013297:Streptococcus pyogenes / Q000201:enzymology / Q000235:genetics*; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008565:Membrane Proteins; D037521:Virulence Factors; D036002:ADP Ribose Transferases