“…In contrast, TSST-1, SPEB, and SPEC share little (generally Ͻ25%), if any, sequence similarity with the other toxins (31). However, despite considerable sequence dissimilarity between TSST-1 and the other SEs, their crystal structures reveal striking similarities in conformational architecture (26,27,36,37). For example, TSST-1 and the other PTSAgs all exhibit a two-domain structure with a C-terminal -grasp motif (domain A), a characteristic N-terminal clawlike  barrel (domain B), and a long diagonal ␣ helix separating these two domains (30,31,38).…”