Flanking DNA-sequences contribute to the specific binding of cI-repressor and OR1.
The binding of cI-repressor to a series of mutant operators containing OR1 of the right operator of bacteriophage lambda was investigated. Sites OR2 and/or OR3 were inactivated by either point or deletion mutations. The free energy of binding repressor to OR1 in the wildtype operator, delta G1, is -13.7 +/- 0.3 kcal/mol. delta G1 determined for an OR2- operator created by a single point mutation in OR2 is -13.6 +/- 0.2 kcal/mol. In contrast, delta G1 for the binding of repressor to a cloned synthetic OR1 operator containing only 24 bp of lambda sequence is -12.2 +/- 0.1 kcal/mol. When sequence 5' to OR1 is present, the binding affinity increases to -13.0 +/- 0.1 kcal/mol. In addition, the proximity of OR1 to a fragment-end decreases delta G1 from -13.7 to -12.3 +/- 0.1 kcal/mol. These results suggest that the DNA sequence outside the 17 bp OR1 binding-site contributes to the specific binding of cI-repressor.
Brenowitz
M
M
Department of Biology, Johns Hopkins University, Baltimore, MD 21218.
Senear
D F
DF
Ackers
G K
GK
D010582:Bacteriophage lambda / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002151:Calorimetry; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009876:Operon; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*; D015183:Restriction Mapping; D014157:Transcription Factors / Q000378:metabolism*; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
D004279:DNA, Viral; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins