title: Hda monomerization by ADP binding promotes replicase clamp-mediated DnaA-ATP hydrolysis.
abstract: ATP-DnaA is the initiator of chromosomal replication in Escherichia coli, and the activity of DnaA is regulated by the regulatory inactivation of the DnaA (RIDA) system. In this system, the Hda protein promotes DnaA-ATP hydrolysis to produce inactive ADP-DnaA in a mechanism that is mediated by the DNA-loaded form of the replicase sliding clamp. In this study, we first revealed that hda translation uses an unusual initiation codon, CUG, located downstream of the annotated initiation codon. The CUG initiation codon could be used for restricting the Hda level, as this initiation codon has a low translation efficiency, and the cellular Hda level is only approximately 100 molecules per cell. Hda translated using the correct reading frame was purified and found to have a high RIDA activity in vitro. Moreover, we found that Hda has a high affinity for ADP but not for other nucleotides, including ATP. ADP-Hda was active in the RIDA system in vitro and stable in a monomeric state, whereas apo-Hda formed inactive homomultimers. Both ADP-Hda and apo-Hda could form complexes with the DNA-loaded clamp; however, only ADP-Hda-DNA-clamp complexes were highly functional in the following interaction with DnaA. Formation of ADP-Hda was also observed in vivo, and mutant analysis suggested that ADP binding is crucial for cellular Hda activity. Thus, we propose that ADP is a crucial Hda ligand that promotes the activated conformation of the protein. ADP-dependent monomerization might enable the arginine finger of the Hda AAA+ domain to be accessible to ATP bound to the DnaA AAA+ domain.
authors.affiliation: Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Su'etsugu
authors.forename: Kenta
authors.initials: K
authors.lastname: Nakamura
authors.forename: Kenji
authors.initials: K
authors.lastname: Keyamura
authors.forename: Yuka
authors.initials: Y
authors.lastname: Kudo
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Katayama
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry*; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000737:chemistry; D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D003062:Codon; D018387:Codon, Initiator; D004247:DNA / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006868:Hydrolysis; D008024:Ligands; D016366:Open Reading Frames; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D001426:Bacterial Proteins; D003062:Codon; D018387:Codon, Initiator; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D029968:Escherichia coli Proteins; D008024:Ligands; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D004247:DNA; D001120:Arginine; C023140:DNA replicase; D004259:DNA-Directed DNA Polymerase; D000251:Adenosine Triphosphatases; C435211:Hda protein, E coli