Determination of biologically active region in toxic shock syndrome toxin 1.

The biologically active areas of toxic shock syndrome toxin 1 (TSST-1) were investigated using chemical fragmentation of the toxin with cyanogen bromide (CNBr). All three main CNBr-generated fragments of TSST-1, with estimated molecular weights of 20,000, 18,000, and 15,000, reacted with monoclonal antibodies (MAbs) 4T, 5T, 6T, 7T, 8T, and 9T, as determined by autoradiography. The epitopes involved in the mitogenic active site were located on the 15,000-Da internal fragment as determined by the neutralization of the mitogenic activity by the MAb. Modification of the methionine residues in the native TSST-1 by alkylation with iodoacetic acid had no effect on the serologic or mitogenic activity.