title: Relaxation complexes of poasmid DNA and protein. III. Association of protein with the 5' terminus of the broken DNA strand in the relaxed complex of plasmid ColE1.
abstract: The location of the protein in the open circular DNA form of the ColE1 DNA-protein relaxation complex, induced by treatment with sodium dodecyl sulfate, has been studied using several enzymes of DNA metabolism. Escherichia coli exonucleases I and III are able to degrade extensively the nicked strand of the relaxed complex from the 3' end. DNA polymerase I can initiate synthesis using the relaxed complex as template-primer and specifically extends the 3' end of the nicked strand. The 5' end of the sodium dodecyl sulfate-relaxed complex, however, is blocked to the 5'-3' hydrolitic action T7 exonuclease. This block remains after trypsin treatment of the sodium dodecyl sulfate-relaxed complex but is removed by Pronase treatment. T4 DNA ligase is unable to seal either the sodium dodecyl sulfate-relaxed complex or the Pronase-treated relaxed complex even after pretreatment of the relaxed complex with T4 DNA polymerase and polynucleotide kinase. However, pretreatment with DNA polymerase I and the four deoxyribonucleoside triphosphates facilitates ligase closure of the Pronase-treated relaxed complex but not the sodium dodecyl sulfate-relaxed complex. These studies indicate that the protein in the relaxed ColE1 complex is located at or near the 5' end of the nicked strand.
mesh_terms: D001426:Bacterial Proteins; D001665:Binding Sites; D002499:Centrifugation, Density Gradient; D004254:DNA Nucleotidyltransferases; D004269:DNA, Bacterial; D004270:DNA, Circular; D003851:Deoxyribonucleases; D004926:Escherichia coli / Q000032:analysis* / Q000201:enzymology; D005092:Exonucleases; D046911:Macromolecular Substances; D009690:Nucleic Acid Conformation; D009876:Operon; D011118:Polynucleotide Ligases; D011402:Pronase; D011485:Protein Binding; D011487:Protein Conformation; D014357:Trypsin
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004270:DNA, Circular; D046911:Macromolecular Substances; D004254:DNA Nucleotidyltransferases; D003851:Deoxyribonucleases; D005092:Exonucleases; D014357:Trypsin; D011402:Pronase; D011118:Polynucleotide Ligases