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. 2013 Oct 4;32(22):2950–2962. doi: 10.1038/emboj.2013.218

Figure 4.

Figure 4

The hinge activates topo IV on negatively supercoiled but not on positively supercoiled DNA. All panels show the relaxation of supercoiled pSG483 plasmid substrate by an equimolar amount of topo IV (500 nM). Negatively supercoiled substrates were used for (A, C, and D). (B) The results for positively supercoiled substrate are shown. In each instance, reactions were quenched midway to prevent full relaxation of the DNA by topo IV alone, so as to determine any effects of MukB (see Supplementary Figure S5 for the corresponding activity time course). Different panels compare different MukB hinge constructs: (A, B) WT MukB hinge; (C) Asp692Phe hinge mutant; (D) AspD692Phe/AspD746Arg/Asp753Arg hinge mutant. Cartoon representations of topoisomer states are shown on the left side of the gels (open circle—relaxed species; intertwined circles—supercoiled species).