TABLE 2.

Reversibility of DNA cleavage

Enzyme	Reversal of plasmid DNA cleavage
	Cip	Cip-Ac	Cip-AcCl	Cip-AcBr
	%
Wild-type gyrase	86.4	87.2	89.2	86.7
GyrA-G81C gyrase	82.5	85.3	4.5	11.9
Topoisomerase IV	88.7	87.3	96.4a	94.5a

^a Note that with topoisomerase IV cleavage by Cip-AcCl and Cip-AcBr is completely reversible even though E. coli topoisomerase IV contains a cysteine at ParC position 82, which corresponds to GyrA position 85. Thus, cross-linkable fluoroquinolones have limited access to regions in helix-IV.