Abstract
The integration host factor (IHF) of Escherichia coli is a small, basic protein that is required for λ site-specific recombination and a variety of cellular processes. It is composed of two subunits, α and β, that are encoded by the himA and hip (himD) genes, respectively. IHF is a sequence-specific DNA-binding protein and bends the DNA when it binds. We have used the bacteriophage P22-based challenge phage selection to isolate suppressor mutants with altered, expanded DNA binding specificities. The suppressors were isolated by selecting mutants that recognize variants of the phage λ H'IHF recognition site. Two of the mutants recognize both the wild-type and a single variant site and contain amino acid substitutions at positions 64 (Pro to Leu) or 65 (Lys to Ser) of the α subunit. These substitutions are in a region of the protein that is predicted to contain a flexible arm that interacts with DNA. Three other mutants, which recognize the wild-type and a different variant site, contain amino acid substitutions at position 44 (Glu to Lys, Val or Gly) of the β subunit. These substitutions are in the middle of a predicted β-strand of the subunit. We discuss the possible mechanisms of suppression by the mutants in terms of a model of the IHF-DNA complex proposed by Yang and Nash [Cell, 57, 869-880 (1989)].
Original language | English (US) |
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Pages (from-to) | 305-313 |
Number of pages | 9 |
Journal | EMBO Journal |
Volume | 11 |
Issue number | 1 |
DOIs | |
State | Published - 1992 |
Keywords
- Altered DNA binding specificity
- IHF
- P22 challenge phage
- Recognition site mutants
- Suppressor mutants
ASJC Scopus subject areas
- General Neuroscience
- Molecular Biology
- General Biochemistry, Genetics and Molecular Biology
- General Immunology and Microbiology