Multiple DNA secondary structures in perfect inverted repeat inserts in plasmids. Right-handed B-DNA, cruciforms, and left-handed Z-DNA.
The capabilities of five recombinant plasmids, containing relatively long (approximately 60-100 base pairs) perfect inverted repeat (IR) inserts, to support supercoil stabilized non-B-DNA structures were studied in vitro. The IRs were also alternating purine-pyrimidine sequences, thus, each could form either left-handed Z-DNA or cruciforms. Single-strand specific endonucleases, restriction endonucleases and methylases, and OsO4 modifications were used to characterize the DNA structures. Two-dimensional gel electrophoretic studies indicated that three of the five IRs formed both cruciforms and Z-DNA. (C-G) containing inserts preferred to form Z-DNA, whereas (T-G) sequences favored cruciforms. In vivo supercoil relaxation experiments demonstrated the existence of cruciforms in Escherichia coli. The physiological significance of these structures is discussed.
Blaho
J A
JA
Department of Biochemistry, School of Medicine, University of Alabama, Birmingham 35294.
Larson
J E
JE
McLean
M J
MJ
Wells
R D
RD
D001483:Base Sequence; D004262:DNA Restriction Enzymes; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000648:ultrastructure*; D004278:DNA, Superhelical / Q000648:ultrastructure; D004926:Escherichia coli / Q000235:genetics*; D007700:Kinetics; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010957:Plasmids
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D004262:DNA Restriction Enzymes