title: Characterisation of opacity factor from group-A streptococci.
abstract: Extracellular opacity factor (OF) from group-A Streptococcus M-type 22 was purified by ammonium sulphate precipitation followed by ion-exchange on DE-52 cellulose and gel filtration on sephacryl S-400. OF was eluted near the void volume and shown to be heterogenous by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Antiserum to ammonium sulphate-purified OF from a cell-free culture supernate was prepared in rabbits. All preparations of OF from supernate and cell-extract were inhibited by the antiserum. No M protein was detected in the OF samples from various purification steps. The purified OF showed activity at a broad pH range with optimal activity at pH 6; it was inactivated considerably at high temperatures. Enzyme activity was inhibited by pepstatin A, but was unaffected by serine proteinase inhibitor, aprotinin, ethylene diamine trichloroacetic acid, N-ethylmaleimide, iodoacetamide and mercaptoethanol. This suggests that OF is an aspartic proteinase.
authors.affiliation: New Zealand Communicable Disease Centre, Porirua.
authors.forename: G A
authors.initials: GA
authors.lastname: Saravani
authors.forename: D R
authors.initials: DR
authors.lastname: Martin
mesh_terms: D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000302:isolation & purification; D011480:Protease Inhibitors / Q000494:pharmacology; D013297:Streptococcus pyogenes / Q000032:analysis* / Q000201:enzymology
chemical_list: D011480:Protease Inhibitors; C021908:opacity factor; D010447:Peptide Hydrolases