Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: UNIPROT:P50502 (
Hip
)
7,003
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Integration host factor (IHF) is a small heterodimeric
DNA-binding protein
of E coli composed of two subunits, alpha and beta, encoded by the himA and hip genes, respectively. IHF binds to DNA at a consensus sequence and bends DNA. HU protein, encoded by the hupA and hupB genes, is similar to IHF except that it does not bind to a specific DNA sequence. To investigate the protein determinants for IHF specificity we exchanged progressively longer segments from the C-terminus of
Hip
with those of HupA, and followed the activity in vivo and in vitro of four such IHF/HU hybrids. Replacement of 11 residues from the C-terminal alpha helix of
Hip
by the complementary eight residues of HupA (hybrid 1), had only minor effects on the DNA binding activity of the protein. As progressively longer segments of
Hip
were replaced by HupA, a precipitous decrease in IHF activity was observed. The hybrid with the longest substitution, hybrid 4, was totally inactive in vivo and could not be purified. None of the hybrid proteins could complement HU activity. Comparing the activities of hybrid 1, hybrid 2 and IHF point mutants, led us to conclude that the structural integrity of the C-terminal alpha helix and its spatial position, but not its amino acid sequence, are important for DNA binding specificity. We favor the hypothesis that alpha helices 3 of both IHF subunits interact with the body of IHF so as to anchor the arms. This interaction stabilizes the arms to permit DNA binding specificity. Thus the C-termini of IHF influence, in an indirect way, the recognition of specific sites on DNA.
...
PMID:Genetic and biochemical analysis of IHF/HU hybrid proteins. 774 38
Integration host factor (IHF) is a small, heterodimeric
DNA-binding protein
of Escherichia coli composed of two subunits, alpha and beta, encoded by the himA and hip genes, respectively. IHF binds to the minor groove at a consensus sequence and bends DNA. We mutagenized the hip gene and studied the activity of the mutant IHF proteins in vivo and in vitro. Substitutions at the C-terminal alpha-helix (alpha-helix 3) reduced IHF activity and relaxed the specificity to DNA without abolishing the ability of IHF to bend DNA. These results indicate that the C-terminal region of
Hip
participates in determining IHF specificity. Alanine substitutions in beta-strands 2 and 3 generally had no effect on IHF activity in vivo suggesting that individually, many of these residues make only small contributions to the binding of IHF to DNA. Replacing the single amino acid of
Hip
that differs from HU in a highly conserved region of the arm did not affect IHF activity. This finding led us to conclude that this region of
Hip
does not contribute to specific DNA recognition by IHF. The binding of IHF to DNA is probably not restricted to one domain, but requires the co-operative participation of a number of regions of the protein.
...
PMID:Genetic and biochemical analysis of the integration host factor of Escherichia coli. 851 42
