Physical characterization of a kinetoplast DNA fragment with unusual properties.

摘要: A 414-base pair fragment from a Leishmania tarentolae kinetoplast DNA minicircle has unusual physical properties. We reported previously that in comparison to phi X174 and pBR322 control fragments, the behaves gel electrophoresis, filtration, electric dichroism experiments as if it an unusually compact conformation. accounted for these properties by proposing is systematically bent helix (Marini, J.C., Levene, S.D., Crothers, D.M., Englund, P.T. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 7664-7668). In this paper, we further explore of fragment. Because its conformation, difficulty snaking through polyacrylamide gels therefore migrates slowly electrophoresis experiments. Warming (53 degrees C) ethanol (5-20%) partially normalize migration; glyoxal treatment results denatured strands with electrophoretic mobility close expected their size. vivo modification does not appear be responsible fragment's properties; anomalous behavior persists after proteinase K treatment, phenol extraction, or cloning into reisolation. Velocity sedimentation rule out aggregation. Secondary structure, such cruciform, detectable S1 mung bean nuclease digestion. The circular spectra characteristic B-type helix. With increasing temperature, there increase 270/280 ellipticity ratio. Circular taken presence show B transition at low concentrations (between 44 54% (w/w]. Thermal denaturation reveals triphasic melting curve.