Site-specific proteolysis of mini-F plasmid replication protein RepE destroys initiator function and generates an...

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• Plasmid F replication relies on a Rep protein with autorepressor and initiator functions.
• The precise mechanism balancing these Rep protein functions for stable replication remains unclear.
• Previous research suggested protein modification might play a role in this control.

Purpose of the Study:

• To investigate the role of protein modification in controlling Plasmid F replication.
• To detect and characterize naturally proteolyzed forms of the F RepE protein.
• To understand how protein processing impacts RepE function and plasmid stability.

Main Methods:

• Detection and biochemical characterization of proteolyzed F RepE protein.
• Assays to evaluate DNA-binding affinity of the processed protein.
• In vivo experiments to assess the effect of the altered protein on F'lac maintenance.

Main Results:

• Naturally proteolyzed F RepE protein was identified and characterized.
• The processed RepE molecule lacks the N-terminal 17 aminoacyl residues and initiator function.
• The altered protein exhibits enhanced specific DNA-binding affinity, particularly with E. coli chromosomal DNA.
• When expressed in trans, the modified RepE protein functions as an incompatibility substance, leading to the elimination of F'lac maintenance.

Conclusions:

• Protein processing of F RepE is a mechanism for regulating plasmid replication.
• The proteolytic cleavage inactivates initiator activity while enhancing DNA-binding.
• This processing contributes to the control of DNA replication by modulating protein function and stability.