M protein of type 12 Strepto coccus pyogenes. Isolation by electrofocusing and some molecular weight-dependent properties.
A method for the isolation and purification of M protein was developed. Purified cell walls were sonically disrupted, solubilized M protein was precipitated by ammonium sulphate and then electrofocused. Both in this material and in hot acid extracts type-specific trypsin-sensitive antigens with two separately precipitating moieties were found. Evidence is adduced showing that they both belong to the M protein complex. The molecular weight of our purified M protein ranged between 400,000 and 20,000 daltons, giving a peak at 150,000 daltons. The pI of this material was found to be 5.4-5.6. There were marked differences between the behaviour of the low, medium and high molecular weight fractions obtained from purified M protein by gel filtration.
D000942:Antigens, Bacterial / Q000032:analysis; D001426:Bacterial Proteins / Q000276:immunology / Q000302:isolation & purification; D002473:Cell Wall / Q000032:analysis; D006868:Hydrolysis; D005779:Immunodiffusion; D007525:Isoelectric Focusing; D008970:Molecular Weight; D013010:Sonication; D013297:Streptococcus pyogenes / Q000032:analysis* / Q000276:immunology / Q000472:pathogenicity; D014774:Virulence
D000942:Antigens, Bacterial; D001426:Bacterial Proteins