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The streptococcal pyrogenic exotoxin (SPE) type B-encoding structural gene, speB, was subcloned from a 4.5-kilobase streptococcal DNA insert onto a 2.4-kilobase insert, which was then sequenced. Studies indicated that a 1,194-base-pair open reading frame encoded a 398-amino-acid protein. Removal of the putative signal peptide resulted in a mature protein with 371 residues (molecular weight, 40,314), which was subsequently proteolyzed to yield a 253-residue breakdown product (molecular weight, 27,588). This processing was confirmed by amino-terminal sequencing of both the 40,314-molecular-weight protein and the breakdown product. Monte Carlo analysis indicated that SPE B was relatively dissimilar to other members of the pyrogenic toxin family that also includes SPEs A and C, toxic shock syndrome toxin 1, and the staphylococcal enterotoxins. Comparison with the published amino acid sequence …