title: Binding of SeqA protein to hemi-methylated GATC sequences enhances their interaction and aggregation properties.
abstract: The SeqA protein regulates chromosome initiation and is involved in segregation in Escherichia coli. One SeqA protein binds to two hemi-methylated GATC sequences to form a stable SeqA-DNA complex. We found that binding induced DNA bending, which was pronounced when the two sequences were on the same face of the DNA. Two SeqA molecules bound cooperatively to each pair of hemi-methylated sites when the spacing between the sites was < or = 30 bp. This cooperative binding was able to stabilize the binding of a wild type to a single hemi-methylated site, or mutant form of SeqA protein to hemi-methylated sites, although such binding did not occur without cooperative interaction. Two cooperatively bound SeqA molecules interacted with another SeqA bound up to 185 bp away from the two bound SeqA proteins, and this was followed by aggregation of free SeqA proteins onto the bound proteins. These results suggest that the stepwise interaction of SeqA proteins with hemi-methylated GATC sites enhances their interaction and leads to the formation of SeqA aggregates. Cooperative interaction followed by aggregation may be the driving force for formation of the SeqA foci that appear to be located behind replication forks.
authors.affiliation: School of Biological Sciences and Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Korea.
authors.forename: Joo Seok
authors.initials: JS
authors.lastname: Han
authors.forename: Sukhyun
authors.initials: S
authors.lastname: Kang
authors.forename: Sung Ho
authors.initials: SH
authors.lastname: Kim
authors.forename: Min Ji
authors.initials: MJ
authors.lastname: Ko
authors.forename: Deog Su
authors.initials: DS
authors.lastname: Hwang
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001665:Binding Sites; D002614:Chelating Agents / Q000494:pharmacology; D003300:Copper / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D007477:Ions; D009154:Mutation; D010618:Phenanthrolines / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D001425:Bacterial Outer Membrane Proteins; D002614:Chelating Agents; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D007477:Ions; D010618:Phenanthrolines; C089746:SeqA protein, E coli; D003300:Copper; D004247:DNA; C025205:1,10-phenanthroline