title: The interaction of the A and A* proteins of bacteriophage phi X174 with single-stranded and double-stranded phi X DNA in vitro.
abstract: The binding of the bacteriophage phi X 174-coded A and A* proteins to single-stranded (ssDNA) and double-stranded (dsDNA ) phi X DNA was studied by electron microscopy. The interaction of the A* protein with ssDNA and dsDNA was also studied by sedimentation velocity centrifugation. It was shown that the binding of the A and A* proteins to ssDNA occurs in a non-cooperative manner and requires no or very little sequence specificity under the conditions used here. Both protein-ssDNA complexes have the same compact structure caused by intrastrand cross-linking through the interaction of protein molecules with separate parts of the ssDNA molecule. The A protein does not bind to phi X dsDNA in the absence of divalent cations. The A* protein does bind to dsDNA, although it has a strong preference for binding to ssDNA. The structure of the A* protein-dsDNA complexes is different from that of the A* protein-ssDNA complexes, as the former have a rosette-like structure caused by protein-protein interactions. High ionic strengths favour the formation of large condensed aggregates.
mesh_terms: D010584:Bacteriophage phi X 174 / Q000235:genetics*; D004277:DNA, Single-Stranded / Q000235:genetics*; D004279:DNA, Viral / Q000235:genetics*; D008854:Microscopy, Electron; D011485:Protein Binding; D011995:Recombination, Genetic; D014764:Viral Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D004277:DNA, Single-Stranded; D004279:DNA, Viral; D014764:Viral Proteins