The Mycoplasma arthritidis superantigen MAM: purification and identification of an active peptide.

The prototypical superantigen MAM is an extracellular T-cell mitogen produced by Mycoplasma arthritidis, an organism which causes chronic proliferative arthritis of rodents. We here describe purification of MAM to homogeneity. Pure MAM exhibits all of the major properties previously described for partially purified MAM, including preference for H-2E molecules in presention to T cells, V beta T-cell receptor specificity for T-cell activation, and in vivo inhibition of T-cell functions but enhancement of B-cell activity as mediated by the superantigen bridge. Edman degradation of pure MAM gave a 54-residue partial amino-terminal sequence. The oligopeptide MAM15-31-C, synthesized according to the Edman sequence, blocked mitogenicity of MAM and supported assignment of the amino acid sequence.