title: Insights into negative modulation of E. coli replication initiation from the structure of SeqA-hemimethylated DNA complex.
abstract: The SeqA protein binds clusters of fully methylated or hemimethylated GATC sequences at oriC and negatively modulates the initiation of DNA replication. We find that SeqA can be proteolytically cleaved into an N-terminal multimerization and a C-terminal DNA-binding domain and have determined the crystal structure of the C-terminal domain in complex with a hemimethylated GATC site. SeqA makes direct hydrogen bonds and van der Waals contacts with the hemimethylated A-T base pair in addition to interactions with the surrounding bases and DNA backbone. The tetrameric protein-DNA complex found in the crystal suggests that SeqA binds multiple GATC sites on separate DNA duplexes, altering the overall DNA topology and sequestering oriC from replication initiation.
authors.affiliation: Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Alba
authors.initials: A
authors.lastname: Guarné
authors.forename: Qinghai
authors.initials: Q
authors.lastname: Zhao
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Ghirlando
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
mesh_terms: D001425:Bacterial Outer Membrane Proteins; D018360:Crystallography, X-Ray; D019175:DNA Methylation; D004261:DNA Replication / Q000502:physiology*; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D018741:Replication Origin; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; C089746:SeqA protein, E coli; D014157:Transcription Factors