title: Binding and bending of the lambda replication origin by the phage O protein.
abstract: We have characterized the binding of lambda phage replication initiation protein O to the phage origin of replication. The minimal DNA segment required for O binding is the single iteron, a 19-bp sequence of hyphenated dyad symmetry that is repeated with variations four times in the origin. The isolated amino terminus of O protein is also sufficient to bind DNA. Electrophoretic studies show that the amino terminus of O protein induces bending of a single iteron. The DNA-protein interaction was characterized by ethylation interference, dimethyl sulfate protection and neocarzinostatin footprinting. Points of DNA-protein contact are largely concentrated in two areas symmetrically disposed with respect to the dyad symmetry of the iteron. This suggests the protein interacts as a dimer with half sites in the DNA. However, a few non-symmetrical contacts are found, indicating that O protein may distort the helix. This may correlate with the bending effects demonstrated electrophoretically. Cylindrical DNA projections were used to model O protein binding to the lambda origin and compare it with the lambda repressor-operator interaction. Whereas bound repressor nearly encircles the DNA in the major groove, O protein leaves the major groove on the opposite side exposed.
mesh_terms: D000478:Alkylation; D010582:Bacteriophage lambda / Q000235:genetics* / Q000648:ultrastructure; D001483:Base Sequence; D001665:Binding Sites; D004261:DNA Replication; D004279:DNA, Viral; D004268:DNA-Binding Proteins / Q000235:genetics*; D009690:Nucleic Acid Conformation; D013463:Sulfuric Acid Esters; D014764:Viral Proteins / Q000235:genetics*; D014779:Virus Replication; D009353:Zinostatin
chemical_list: D004279:DNA, Viral; D004268:DNA-Binding Proteins; D013463:Sulfuric Acid Esters; D014764:Viral Proteins; D009353:Zinostatin; C007482:dimethyl sulfate