SpyA is a membrane-bound ADP-ribosyltransferase of Streptococcus pyogenes which modifies a streptococcal peptide, SpyB

• Published in: Molecular microbiology Vol. 83; no. 5; pp. 936 - 952
• Main Authors: Korotkova, Natalia, Hoff, Jessica S., Becker, Devon M., Quinn, John Kyle Heggen, Icenogle, Laura M., Moseley, Steve L.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.03.2012; Blackwell
• Subjects: ADP Ribose Transferases - genetics; ADP Ribose Transferases - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; DNA, Bacterial - genetics; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Bacterial; Membrane Proteins - genetics; Membrane Proteins - metabolism; Membranes; Microbiology; Miscellaneous; Mutagenesis, Site-Directed; Operon; Plasmids; Protein Structure, Secondary; Proteins; Streptococcus infections; Streptococcus pyogenes; Streptococcus pyogenes - enzymology; Streptococcus pyogenes - genetics; Virulence Factors - genetics; Virulence Factors - metabolism; Streptococcaceae; ADP ribosylation; Gene; Peptides; Enzyme; Bacteria; Micrococcales; Streptococcus pyogenes
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2012.07979.x

Summary 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.