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Oriented DNA binding by one‐armed λ repressor heterodimers and contacts between repressor and RNA polymerase at P RM
Author(s) -
Kim YongIn,
Hu James C.
Publication year - 1997
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1997.4651831.x
Subject(s) - repressor , rna polymerase , biology , microbiology and biotechnology , protein subunit , transcription (linguistics) , leucine zipper , polymerase , operator (biology) , dna , rna , transcription factor , gene , genetics , linguistics , philosophy
Bacteriophage λ repressor activates transcription from P RM by contacting the σ subunit of E. coli RNA polymerase. Although mutations in repressors that are defective in activation affect exposed residues in the repressor–operator co‐crystal, the subunit in repressor dimers that is responsible for activation has not been determined experimentally. Here, we describe an oriented heterodimer approach using one‐armed repressor–leucine zipper fusion proteins to resolve this question. Protection against methylation of operator DNA in vitro by one‐armed and two‐armed repressor–leucine zipper heterodimers shows that the subunit containing the arm in a one‐armed repressor heterodimer binds preferentially in the consensus half‐site of λ operators. The patterns of activation of the P RM promoter in vivo by one‐armed heterodimers containing the pc2 mutation in only one subunit show that RNA polymerase at P RM contacts the N‐terminal domain of the promoter‐proximal subunit of the repressor dimer.