Enzymatic digestion of operator DNA in the presence of the lac repressor tryptic core.
The trypsin-resistant core protein of the lac repressor was utilized in protecting operator DNA from two types of enzymatic digestion. Core repressor protects and enhances operator DNA digestion by DNase I in the same fashion as intact repressor, though to a lesser degree on the lower strand. DNase I patterns found for the ternary complexes (protein-sugar-operator) were consistent with the expected affinity alterations of the protein species in response to binding these ligands. The 3' boundaries obtained by exonuclease III digestion for the intact repressor-operator complex varied slightly from those reported by Shalloway et al. (1980). Asymmetric binding to operator by the core repressor fragment was suggested by differences in the 3' boundary for the core compared to intact repressor on the promoter-distal side of the complex. A composite picture of repressor structure and function emerges from the protection studies reported here and in the accompanying paper. In light of these and other results, models for repressor binding are examined.
D001345:Autoradiography; D001483:Base Sequence; D004269:DNA, Bacterial / Q000378:metabolism*; D003850:Deoxyribonuclease I; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000032:analysis; D005090:Exodeoxyribonucleases; D007763:Lac Operon; D008958:Models, Molecular; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014357:Trypsin
D004269:DNA, Bacterial; D012097:Repressor Proteins; D014157:Transcription Factors; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III; D003850:Deoxyribonuclease I; D014357:Trypsin