M protein of type 12 Strepto coccus pyogenes. Isolation by electrofocusing and some molecular weight-dependent properties.

  • 1 January 1975
    • journal article
    • research article
    • Vol. 42  (3) , 147-58
Abstract
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.

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