title: Energy storage during DNA girase activity.
abstract: In this work, we develop a minimal two-cycle model for the action of DNA girase. One of the cycles describes the ATP dependent chemicomechanical transduction performed by the enzyme. The other cycle describes the relaxing activity exhibited by girase on supercoiled DNA in the absence of substrates. Supercoiling of DNA is described as a random walk on a topological index. The mechanical energy storage in DNA is manifested in the fact that in general, the kinetic constants for the cycles do not satisfy Wegscheider relations. Finally, a connection is established between the degree of DNA supercoiling and the hydrolysis of ATP.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism; D004734:Energy Metabolism; D004926:Escherichia coli / Q000201:enzymology; D007700:Kinetics; D008954:Models, Biological; D013816:Thermodynamics
chemical_list: D004278:DNA, Superhelical; D000255:Adenosine Triphosphate; D004250:DNA Topoisomerases, Type II