[Isolation and characterization of erythrogenic toxins. VIII. Purification of a biologically active protein of the molecular weight 10,000 (LMP-10k) from filtrates of Streptococcus pyogenes, strain NY-5. Relationship to erythrogenic toxin type A].

The "classical" method for purification of erythrogenic toxin type A results in two products: erythrogenic toxin type A and a low molecular weight protein, m.w. 10,000 (LMP-10k) with mitogenic activities. LMP-10k was purified from culture supernatants of S. pyogenes (group A) by CM-Sepharose CL-6B chromatography and Sephacryl S-200 and Sephadex G75 gel filtration to a high degree of purity with minimal amounts of residual erythrogenic toxin A. The isoelectric point of LMP-10k is the same as for erythrogenic toxin A: 5.2. The immunogenic activity is low, only one of two rabbits produced anti-LMP-10k-antibodies after a prolonged course of immunization. On the other hand it is possible to induce antierythrogenic toxin A-antibodies by immunization with LMP-10k preparations contaminated with small amounts of erythrogenic toxin A. Possibly the data given by some authors for the m.w. of erythrogenic toxin type A as 8 000 D are the results of a mix-up with co-purified LMP-10k.