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A conformational switch between transcriptional repression and replication initiation in the RepA dimerization
Rafael Giraldo1, Carlos Fernández-Tornero, Philip R Evans
1Department of Molecular Microbiology Centro de Investigaciones Biológicas-CSIC, C/ Velázquez 144, Madrid, 28006, Spain. rgiraldo@cib.csic.es
Nature Structural Biology
|May 27, 2003
Summary
The study reveals the crystal structure of a dimeric initiator protein domain (dRepA), crucial for plasmid DNA replication in bacteria. This structure clarifies how Rep proteins activate DNA replication initiation.
Area of Science:
- Molecular Biology
- Microbiology
- Structural Biology
Background:
- Plasmids facilitate gene transfer in bacteria.
- Plasmid DNA replication initiation involves initiator proteins (Rep) binding to origin sequences.
- Rep proteins regulate their own gene transcription through dimerization and DNA binding.
Purpose of the Study:
- To determine the molecular mechanism of Rep protein activation.
- To elucidate the structure of the dimeric N-terminal domain of the pPS10 plasmid initiator (dRepA).
Main Methods:
- X-ray crystallography to determine the three-dimensional structure of dRepA.
- Structural comparison with homologous proteins like monomeric RepE (mRepE).
Main Results:
- The crystal structure of dimeric RepA (dRepA) was determined, revealing a winged-helix fold.
- Dimerization induces a conformational change, transforming an interdomain loop and beta-strand in monomeric RepE into an alpha-helix in dimeric RepA.
- dRepA shares structural similarities with the C-terminus of eukaryotic and archaeal Cdc6 proteins.
Conclusions:
- The study provides the first structural insights into the dimeric state of a Rep initiator protein.
- The findings offer clues into the activation mechanism of Rep proteins and the evolutionary relationships of DNA replication initiators.