Determination of the primary target of a quinolone drug and the effect of quinolone resistance-conferring mutations by measuring quinolone sensitivity based on its mode of action.

We used an assay to measure quinolone sensitivity as a shift in the position of the cleavage-religation equilibrium. This assay was found to be useful in identifying the primary target of a quinolone drug and assessing the effect of quinolone resistance-conferring mutations.

Replacement of ParC alpha4 helix with that of GyrA increases the stability and cytotoxicity of topoisomerase IV-quinolone-DNA ternary complexes.

Replacement of the alpha4 helix of ParC with that of GyrA increased the stability of topoisomerase IV-quinolone-DNA ternary complexes. This mutant topoisomerase IV-mediated cell killing was more efficient than topoisomerase IV-mediated cell killing in Escherichia coli. Thus, the alpha4 helix plays critical roles in determining the stability and the cytotoxicity of ternary complexes.

Localization of functional endothelin receptor signaling complexes in cardiac transverse tubules.

Endothelin-1 (ET-1) is an autocrine factor in the mammalian heart important in enhancing cardiac performance, protecting against myocardial ischemia, and initiating the development of cardiac hypertrophy. The ETA receptor is a seven-transmembrane G-protein-coupled receptor whose precise subcellular localization in cardiac muscle is unknown. Here we used fluorescein ET-1 and 125I-ET-1 to provide evidence for ET-1 receptors in cardiac transverse tubules (T-tubules).