A novel protein binds a key origin sequence to block replication of an E. coli minichromosome.
A sequence of three tandem repeats of a 13-mer in the replication origin (oriC) of E. coli is the highly conserved site of opening of the duplex for initiation of DNA synthesis. A protein that binds this sequence has been discovered in E. coli and purified to homogeneity. This novel 33 kd polypeptide behaves as a dimer. Binding to the 13-mers is specific and limited to this region. At a ratio of 10-20 monomers per oriC plasmid, the binding blocks initiation by preventing the opening of the 13-mer region by dnaA protein. Once the 13-mers are opened by dnaA protein action, the 33 kd protein is without effect on the subsequent stages of replication. The specificity of binding and profound inhibitory effect suggest a regulatory role for this protein at an early stage of chromosome initiation.
Department of Biochemistry, Stanford University School of Medicine, California 94305-5307.
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Hwang
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Kornberg
D001483:Base Sequence; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D002876:Chromosomes, Bacterial; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D003850:Deoxyribonuclease I; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D015345:Oligonucleotide Probes; D010957:Plasmids; D015183:Restriction Mapping
D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D015345:Oligonucleotide Probes; D003850:Deoxyribonuclease I