Difference between revisions of "Part:BBa K200003"

Revision as of 09:21, 29 September 2009

Rfal
Waal ligase is an enzyme responsible for the ligation of an O-antigen to the core oligosaccharide in the Gram-negative bacterium's outer membrane.

Unlike other exopolysaccharides, colanic acid does not naturally bind to the cell surface but rather forms a thick mesh between cells. While Waal Ligase usually links the O-antigen to the core oligosaccharide, in K-12 it links colanic acid to the core oligosaccharide. This is because E.coli K-12 does not produce O-antigen due to an insertion mutation.

Usage and Biology

Figure 1: LPS structure (source: [http://en.wikipedia.org/wiki/O_antigen wikipedia])

LipoPolySaccharyde is a major component of the outer cell wall in Gram-negative bacteria. It is constituted of three main components: the O-antigen, the core polysaccharides and the lipid A (see Fig. 1).
The O-antigen is a highly variable chain of polysaccharydes and is physically linked to the core.
The core component is made up of a short chain of sugars (oligosaccharide) and is linked to both the O-antigen and the Lipid A components of the cell wall.
The Lipid A component of the LPS contains fatty acid chains which causes the LPS to dock into the outer membrane of the Gram-negative bacterium.
In the majority of E.coli, the enzyme Rfal joins the O-antigen to the membrane-bound lipid core molecule. Since the K-12 strain has an insertion mutation in the gene coding for O-antigen, the enzyme Rfal is free to join colanic acid to the lipid core.

The gene was used as part of the Imperial iGEM 2009 The E.ncapsulator project to join the colanic acid to the lipid core.

Sequence and Features

Requirements

• Gram-negative bacterium
• Colanic acid producing gene (rcsB)

References

<biblio>

1. function pmid=15838026
2. Function2 pmid=19019161
3. Function3 pmid=15215252

</biblio>