YacG inhibits all the catalytic activities of DNA gyrase by preventing its interaction with DNA. It acts by binding directly to the C-terminal domain of GyrB, which probably disrupts DNA binding by the gyrase [1]. YacG has been shown to bind zinc and contains the structural motifs typical of zinc-binding proteins [2]. The conserved four cysteine motif in this protein (-C-X(2)-C-X(15)-C-X(3)-C-) is not found in other zinc-binding proteins with known structures.

1: YacG from Escherichia coli is a specific endogenous inhibitor of DNA gyrase. Sengupta S, Nagaraja V; Nucleic Acids Res. 2008;36:4310-4316. PMID:18586829

2: NMR structure of the Escherichia coli protein YacG: a novel sequence motif in the zinc-finger family of proteins. Ramelot TA, Cort JR, Yee AA, Semesi A, Edwards AM, Arrowsmith CH, Kennedy MA; Proteins. 2002;49:289-293. PMID:12211008