FIGURE 2.

Comparison of two TetR family members bound to cognate DNA. A, structure of the Ms6564-operator complex. This view is that of Fig. 1B rotated by 90°. Ribbons represent proteins; sticks represents DNA. B, structure of the QacR-DNA complex. This view is same as that in A. C, comparison of the relative depths of two recognition helices into the DNA major groove. In the Ms6564-DNA complex (upper panel), the recognition helix is inserted only slightly into the major groove. In contrast, the recognition helix of QacR sinks deeply into the major groove floor (lower panel). Cylinders represent proteins, and tubes represent DNA.