title: DNA-binding properties of the Erf protein of bacteriophage P22.
abstract: The phage P22 erf (essential recombination function) gene was placed in a small plasmid under the control of a strong, inducible promoter by manipulations in vitro. Erf protein was purified from induced cells, and characterized. Erf protein (monomer molecular weight 23,000) forms oligomers in solution. The carboxyl terminus is protease-sensitive: its removal generates a discrete amino-terminal fragment (molecular weight approximately 18,000) that also oligomerizes. At temperatures below 45 degrees C, Erf forms stable, discrete complexes with single-stranded DNA and supercoiled DNA, but not with relaxed double-stranded DNA. Binding to single-stranded DNA is stoichiometric; one Erf monomer binds approximately 15 bases of DNA, over the range of protein concentrations tested (2 to 100 micrograms/ml). At high temperatures (50 to 60 degrees C). Erf binds single- and double-stranded DNA, forming aggregates instead of discrete complexes. Heating and cooling in the absence of DNA produces a form of Erf that has single-stranded binding specificity, but forms aggregates on binding.
mesh_terms: D004265:DNA Helicases / Q000032:analysis; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D004720:Endonucleases / Q000378:metabolism; D008970:Molecular Weight; D010957:Plasmids; D012483:Salmonella Phages / Q000378:metabolism*; D015719:Single-Strand Specific DNA and RNA Endonucleases; D014764:Viral Proteins / Q000032:analysis*
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D014764:Viral Proteins; D004720:Endonucleases; D015719:Single-Strand Specific DNA and RNA Endonucleases; D004265:DNA Helicases