title: Stepwise assembly of a relaxosome at the F plasmid origin of transfer.
abstract: A central step in the transfer of genetic information during bacterial conjugation of the Escherichia coli F plasmid involves the formation of a protein-DNA complex, called the relaxosome, at the origin of transfer. During conjugation, the relaxosome introduces a site- and strand-specific nick from which the physical transfer of a single strand of DNA is initiated. At least two F-encoded proteins, TraIp (traI gene product) and TraYp (traY gene product), and one host-encoded protein, integration host factor, are involved in this process. In this report, we use DNase I protection and electron microscopic techniques to investigate the mechanism of relaxosome formation. Our results show that TraYp and integration host factor form a protein-DNA complex that facilitates the binding of TraIp to assemble a relaxosome capable of introducing a site- and strand-specific nick at the origin of transfer. This nick is identical to that observed during conjugation.
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism; D001665:Binding Sites; D002874:Chromosome Mapping; D003227:Conjugation, Genetic; D004265:DNA Helicases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D004720:Endonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D005144:F Factor / Q000302:isolation & purification / Q000378:metabolism; D005798:Genes, Bacterial; D034982:Integration Host Factors
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D034982:Integration Host Factors; C063238:traY protein, E coli; D004720:Endonucleases; C027093:TraI protein, E coli; D004265:DNA Helicases