Control of ColE1 plasmid replication. Interaction of Rom protein with an unstable complex formed by RNA I and RNA II.
A transcript (RNA I) from ColE1 inhibits initiation of replication of the plasmid DNA by binding to the precursor of the primer RNA (RNA II). The ability of RNA I to inhibit replication is altered by the presence of a plasmid-specified small protein, Rom. In vitro, RNA I binds to RNA II to form a very unstable complex, C*. Binding of a single molecule of Rom converts C* to a more stable complex, Cm*. Each of these complexes, C* or Cm*, transforms to a more stable complex, C** or Cm**, respectively. While formation of complex C* or Cm* is inferred from the inhibition of binding caused by a second RNA I species, that of complex C** or Cm** is detected by alteration of RNase sensitivity. Complex C* converts to complex Cm* very rapidly upon addition of Rom to the medium and complex Cm* converts to complex C* very rapidly by removal of Rom from the medium. On the other hand, complexes C** and Cm** do not rapidly interconvert, but can eventually transform to the same stable final product. Thus, Rom affects binding of RNA I to RNA II through conversion of a very unstable early intermediate to a more stable complex, creating a second pathway for their stable binding.
Tomizawa
J
J
Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
D001426:Bacterial Proteins / Q000378:metabolism*; D003086:Bacteriocin Plasmids; D004261:DNA Replication; D004269:DNA, Bacterial / Q000096:biosynthesis; D004926:Escherichia coli / Q000235:genetics; D006207:Half-Life; D007700:Kinetics; D010957:Plasmids; D012313:RNA / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism; D012329:RNA, Bacterial / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C042027:RNA I; D012322:RNA Precursors; C034477:RNA primers; D012329:RNA, Bacterial; C042833:ROM protein, Bacteria; D012313:RNA; D012260:Ribonucleases