Open AccessSUPERCOILED CIRCULAR DNA-PROTEIN COMPLEX IN Escherichia coli : PURIFICATION AND INDUCED CONVERSION TO AN OPEN CIRCULAR DNA FORM
Author(s) -
Don B. Clewell,
Donald R. Helinski
Publication year - 1969
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.62.4.1159
Subject(s) - sedimentation coefficient , dna supercoil , dna , centrifugation , sodium dodecyl sulfate , escherichia coli , sedimentation , biology , pronase , biophysics , trypsin , biochemistry , microbiology and biotechnology , chemistry , dna replication , enzyme , gene , paleontology , sediment
The 23S twisted circular form ofCol E1 DNA has been isolated fromEscherichia coli as a tightly associated DNA-protein complex with a sedimentation coefficient of approximately 24S . Treatment of this complex with pronase, trypsin, sodium dodecyl sulfate, Sarkosyl, or heat results in a conversion to a slower sedimenting form of 17S or 18S , as determined by centrifugation in neutral sucrose gradients. These treatments do not alter the sedimentation properties of noncomplexes supercoiledCol E1 DNA even in the presence of theCol E1 -protein complex. Electron microscopic analyses indicate that the decrease in sedimentation rate of theCol E1 -protein complex after treatment with these various agents is largely owing to an induced transition ofCol E1 DNA from the supercoiled to the open circular state.