title: Domain structure and quaternary organization of the bacteriophage P22 Erf protein.
abstract: The structure and activities of the recombination-promoting P22 Erf protein were examined in vitro. Treatment of the protein with elastase produces a stable amino-terminal fragment, consisting of amino acid residues 1 to (approximately) 136. We have purified this fragment, designated fragment B, to apparent homogeneity by gel filtration chromatography. Fragment B retains the oligomeric structure and single-stranded DNA binding specificity of intact Erf. It differs, however, in lacking the ability of intact Erf to bind single-stranded DNA into large aggregates following mild heat treatment of the protein. In addition, its binding to DNA may be weaker than that of intact Erf. Intact Erf sediments through a sucrose gradient as a discrete species with an apparent S20,w of approximately 11 X 7 S. Its sedimentation behavior is affected little, if at all, by concentration. Fragment B also sediments as a discrete species at approximately 10 X 4 S. In the electron microscope, intact Erf appears as rings, with 10 to 14 small projecting structures resembling the teeth of a gear. Fragment B is similar, except that it appears to lack the peripheral structures. From these observations, we conclude that Erf consists of at least two structurally and functionally distinct domains, and that it has a discrete ring-like oligomeric structure.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D004277:DNA, Single-Stranded; D004591:Electrophoresis, Polyacrylamide Gel; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D010446:Peptide Fragments / Q000302:isolation & purification; D011487:Protein Conformation; D011995:Recombination, Genetic; D012483:Salmonella Phages / Q000032:analysis*; D014764:Viral Proteins / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D004277:DNA, Single-Stranded; D046911:Macromolecular Substances; D010446:Peptide Fragments; D014764:Viral Proteins