FIG. 1.

Overview of the ComK-binding site (K-box) in B. subtilis. (A) Schematic representation of a K-box. A K-box consists of two AT-boxes (shaded gray) with the consensus sequence AAAA-(N)₅-TTTT. In this study, the AT-box closest to the −35 position is indicated as AT-box 1, while the box further upstream is called AT-box 2. In each AT-box, the positions of the four A's and T's are indicated with subscript numbers. The three distinguished classes of K-boxes (C I, C II, and C III) are indicated with the lengths of their respective spacers. The average AT content of the spacer region is over 60%. (B) Helical representation of a K-box. In this figure, a class I K-box with a spacer of two helical turns is depicted in a helical projection. The dark vertical bars represent the AT base pairs in the AT boxes. The gray circles represent the (A)₄ stretches, and the black circles represent the (T)₄ stretches in both AT-boxes.