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

Abstract

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.

A Group A Streptococcus ADP-Ribosyltransferase Toxin Stimulates a Protective Interleukin 1β-Dependent Macrophage Immune Response

“…Our use of the AP ( covS mutant) GAS strain focused our attention on the bloodstream stage of the infection, and our data should not be extrapolated to suggest that SpyA stimulates GAS clearance at other distinct stages or foci of infection. Researchers who performed earlier studies speculated that in early, localized infections, SpyA effects that cause epithelial cell damage such as cytoskeletal protein rearrangement and programmed cell death ( 9 , 10 , 12 ) may promote survival within a skin abscess. Furthermore, during the initial stages of colonization and mucosal infection (e.g., pharyngitis), it is possible that GAS activation of host inflammatory responses results in preferential clearance of normal microflora, upon which the pathogen with its larger arsenal of immune resistance factors can occupy the evacuated niche, similar to a recent paradigm shift in our understanding of Salmonella gastrointestinal infection ( 36 , 37 ).…”

“…One gene that is highly upregulated upon covRS mutation in M1T1 GAS is spyA , encoding a membrane-bound C3-like ADP-ribosyltransferase capable of catalyzing the covalent transfer of an ADP ribose moiety of NAD + to target proteins ( 8 – 10 ). Several ADP-ribosyltransferase toxins of pathogenic bacteria, including Pseudomonas exotoxin A, cholera toxin, and diphtheria toxin, are associated with host cell death (reviewed in reference 11 ).…”

Novel bacterial ADP-ribosylating toxins: structure and function

“…Unexpectedly, SpyA was not detected in S. pyogenes culture supernatants; instead the predicted leader sequence formed a transmembrane helix and was inserted into the bacterium outer membrane 144 . SpyA contains a C3-like RSE motif with the predicted catalytic Glu at position 187 143 .…”

The Globally Disseminated M1T1 Clone of Group A Streptococcus Evades Autophagy for Intracellular Replication

“…Strain M6 JRS4 + pSpeB was constructed by introducing plasmid pSpeB (Korotkova et al, 2012) into M6 JRS4 by electroporation.…”