Figure 8.

The GyrA red acidic tail controls of species-specific supercoiling. (A) Sequences of the GyrA C-terminal acidic amino acids (red) for E. coli and Salmonella Typhimurium. (B) Proposed mechanism to control supercoiling at different locations. Supercoiling is illustrated for a plasmid with a Mu SGS DNA binding site. The long arm (Brown) interacts with one gyrA pinwheel element, the gate segment (Aqua) folds into the upper chamber, and the right arm (Purple) interacts extensively with opposite pinwheel elements. The T segment (Green) passes through the open DNA gate during strand transfer. See text for step details.