Nucleotide sequence of the R721 shufflon

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• The shufflon is a DNA region known for complex rearrangements.
• These rearrangements are mediated by a site-specific recombinase, RCI.
• Previous studies identified shufflon segments in IncI1 plasmid R64.

Purpose of the Study:

• To determine the DNA sequences of the shufflon region and the rci gene of IncI2 plasmid R721.
• To analyze the structure of the R721 shufflon and its potential function.
• To characterize the RCI protein encoded by the R721 rci gene.

Main Methods:

• DNA sequencing of the shufflon region and rci gene.
• Structural analysis of open reading frames (ORFs).

Main Results:

• The DNA sequences of the IncI2 plasmid R721 shufflon and its rci gene were determined.
• The R721 shufflon contains three invertible DNA segments, homologous to those in IncI1 plasmid R64.
• Structural analysis suggests the R721 shufflon acts as a biological switch for selecting one of six pilV genes.

Conclusions:

• The RCI protein from IncI2 plasmid R721 is a basic protein of 374 amino acids.
• The R721 shufflon likely functions as a biological switch, controlling pilV gene expression.
• This mechanism allows for variation in the C-terminal region of pilV genes while maintaining a constant N-terminal region.