Structure of the replication terminus-terminator protein complex as probed by affinity cleavage

Area of Science:

• Molecular Biology
• Structural Biology
• Genetics

Background:

• Replication terminator protein (RTP) from Bacillus subtilis is a homodimer that regulates DNA replication fork progression.
• RTP impedes replication fork movement unidirectionally at the replication terminus.
• Understanding the three-dimensional structure of the RTP-DNA complex is crucial for explaining functional asymmetry from symmetrical protein dimers.

Purpose of the Study:

• To determine the three-dimensional structure of the Bacillus subtilis RTP-DNA complex.
• To elucidate how symmetrical RTP dimers generate functional asymmetry in DNA replication termination.
• To map the specific contacts between RTP and terminus DNA.

Main Methods:

• Converted RTP into a site-directed chemical nuclease to probe DNA-protein interactions.
• Analyzed base-specific DNA cleavage patterns to identify amino acid-to-base contacts.
• Utilized crystal structure of RTP and mapped contacts as distance constraints to build a DNA-protein complex model.

Main Results:

• Mapped specific amino acid-to-base contacts within the RTP-DNA complex.
• Developed a structural model of the functional unit of the replication terminus, comprising four DNA turns and two interacting RTP dimers.
• Provided insights into the mechanism of directional replication termination.

Conclusions:

• The developed model explains the functional asymmetry of RTP despite its symmetrical dimer structure.
• The study provides a structural basis for understanding DNA replication termination mechanisms.
• The findings have implications for controlling DNA replication processes.