FIG. 5.

Stereo representation of the gate region of E. coli DNA gyrase breakage-reunion domain (RCSB Protein Data Bank accession no. 1AB4) with helix 4 shown in ribbon format. The catalytic tyrosine and the residues that are mutated to effect NXL101 or fluoroquinolone resistance are rendered in ball-and-stick mode. In S. aureus numbering, these are Val45, His80, Asp83, Arg92, Ala94, and Met121 (NXL101 resistance) and Ser84 and Asp/Glu88 (fluoroquinolone resistance). The terminal atoms of the Met121 and Asp83 side chains show van der Waals spheres.