Coming Across The Ideal selleck Package

However, (?) supercoiling of the catenanes nearly completely blocks the unlinking. The mechanism of the phenomenon becomes clear from the conformation of (?) supercoiled catenanes shown in Fig.?3. We see from the figures that (?) supercoiled interwound branches are pushed out from the region where two DNA molecules interwind. Because the enzyme-bound G-segments are strongly bent, the G-segment appears at one of the apices of interwound branches very soon after the binding ( Fig.?7B). This phenomenon, the localization of strongly bent elements at the apices of the interwound DNA superhelix, where DNA has to be bent in any case, is well known from both experimental and theoretical studies ( 43, 44?and?45). Such localization of the bent G-segment makes nearly impossible its juxtapositions with Temsirolimus concentration a potential T-segment that has to be inside the apex. The corresponding probability is so small that we were only able to estimate that it is MRIP with the bent G-segment is ?20-times lower than the probability of interchain juxtaposition (for ??= 0.08 and ��?= 0.03). Our computational analysis showed that the mode of type IIA DNA topoisomerase action makes (+) supercoiled DNA catenanes much more favorable for unlinking than (?) supercoiled catenanes. This gives us one more example of how protein-induced DNA bending can strongly affect enzymatic topological transformations of DNA molecules. It was shown that the magnitude of the protein-induced bend can dramatically change topological outcomes of the site-specific recombination (45). A protein-induced DNA bend postulated in the model of topo IIA topoisomerase action was intended to explain the amazing ability of the enzymes to reduce the steady-state Selleckchem PD173074 fractions of knots and links in circular DNA many times below the corresponding equilibrium fractions (40?and?46). Later the G-segment bending was proven experimentally (24, 40, 41?and?47), and Roca and Wang (42) had established the second key feature of the model: the unidirectional transport of the T-segment through the enzyme. Thus, both features of the suggested model, consisting of the protein-induced bending of the G-segment and the unidirectional transport from inside the bend to the outside, were proven.