Increased temperature and 2-methyl-2,4-pentanediol change the DNA structure of both curved and uncurved adenine/thymine-rich sequences.
DNA curvature is affected by elevated temperature and dehydrating agents such as 2-methyl-2,4-pentanediol (MPD) (used in crystallization). This effect of MPD has been ascribed to a specific distortion of the structure of adenine tracts (A-tracts), probably through a deformation of the characteristic narrow minor groove. Uranyl photoprobing indicates that a narrowed minor groove is present in all A/T regions containing four or more A/T base pairs. Consequently, this technique may be employed to study conformational changes in other A/T-rich sequences than pure A-tracts. In this study we use uranyl photoprobing to demonstrate that the effect of elevated temperature and MPD is analogous on both "normal" and curve-inducing A/T-rich sequences. The results therefore indicate that under these conditions the minor groove is widened in all A/T sequences and not only in pure A-tracts as previously suggested. Thus, the rather subtle structural difference of AT regions and A-tracts in nonbent DNA versus A-tracts in bent DNA may be quantitative rather than qualitative; i.e., the structure is more persistent and/or rigid in bent DNA.
Møllegaard
Niels Erik
NE
Department of Medical Biochemistry and Genetics, The Panum Institute, University of Copenhagen, Blegdamsvej 3c, 2200 Copenhagen N, Denmark. nem@imbg.ku.dk
Nielsen
Peter E
PE
D000225:Adenine; D001482:Base Composition; D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000187:drug effects; D018105:DNA, Kinetoplast / Q000737:chemistry / Q000187:drug effects; D006018:Glycols / Q000494:pharmacology*; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000737:chemistry* / Q000187:drug effects; D013816:Thermodynamics; D013941:Thymine
D018105:DNA, Kinetoplast; D006018:Glycols; D004247:DNA; D000225:Adenine; C011480:hexylene glycol; D013941:Thymine