Structure and function of DnaA N-terminal domains: specific sites and mechanisms in inter-DnaA interaction and in DnaB helicase loading on oriC

• Published in: The Journal of biological chemistry 2007-06, Vol.282 (24), p.17816-17827
• Main Authors: Abe, Yoshito, Jo, Takaaki, Matsuda, Yusaku, Matsunaga, Chika, Katayama, Tsutomu, Ueda, Tadashi
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Binding Sites; DNA - chemistry; DNA - metabolism; DNA Replication; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; DnaB Helicases - chemistry; DnaB Helicases - genetics; DnaB Helicases - metabolism; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Models, Molecular; Molecular Sequence Data; Origin Recognition Complex; Protein Structure, Quaternary; Protein Structure, Tertiary
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M701841200

DnaA forms a homomultimeric complex with the origin of chromosomal replication (oriC) to unwind duplex DNA. The interaction of the DnaA N terminus with the DnaB helicase is crucial for the loading of DnaB onto the unwound region. Here, we determined the DnaA N terminus structure using NMR. This region (residues 1-108) consists of a rigid region (domain I) and a flexible region (domain II). Domain I has an alpha-alpha-beta-beta-alpha-beta motif, similar to that of the K homology (KH) domain, and has weak affinity for oriC single-stranded DNA, consistent with KH domain function. A hydrophobic surface carrying Trp-6 most likely forms the interface for domain I dimerization. Glu-21 is located on the opposite surface of domain I from the Trp-6 site and is crucial for DnaB helicase loading. These findings suggest a model for DnaA homomultimer formation and DnaB helicase loading on oriC.