title: Characterization of a complement-binding protein, DRS, from strains of Streptococcus pyogenes containing the emm12 and emm55 genes.
abstract: An extracellular protein of Streptococcus pyogenes, streptococcal inhibitor of complement (SIC), and its variant, called DRS (distantly related to SIC), are expressed by some S. pyogenes strains. SIC from type 1 (M1) isolates of S. pyogenes interferes with complement-mediated cell lysis, reportedly via its interaction with complement proteins. In this study we demonstrate that S. pyogenes strains carrying emm12 and emm55 (the genes for the M12 and M55 proteins, respectively) express and secrete DRS. This protein, like SIC, binds to the C6 and C7 complement proteins, and competition enzyme-linked immunosorbent assay experiments demonstrate that DRS competes with SIC for C6 and C7 binding. Similarly, SIC competes with DRS for binding to the complement proteins. Despite this, the recombinant DRS preparation showed no significant effect on complement function, as determined by lysis of sensitized sheep erythrocytes. Furthermore, the presence of DRS is not inhibitory to SIC activity.
authors.affiliation: Queensland Institute of Medical Research, 300 Herston Road, Herston, Queensland 4006, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Binks
authors.forename: K S
authors.initials: KS
authors.lastname: Sriprakash
mesh_terms: D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000235:genetics* / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003183:Complement C6 / Q000378:metabolism; D003184:Complement C7 / Q000378:metabolism; D006461:Hemolysis / Q000502:physiology; D008969:Molecular Sequence Data; D013297:Streptococcus pyogenes / Q000235:genetics* / Q000378:metabolism
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003183:Complement C6; D003184:Complement C7; C095209:Emm55 protein, Streptococcus pyogenes; C097739:SIC protein, Streptococcus