Difference between revisions of "Part:BBa K5246027"

Revision as of 08:07, 29 September 2024

CB2/CB2A HfsJ Glycosyltransferase, 6xHis tag for purification

Introduction

Vilnius-Lithuania iGEM 2024 project Synhesion aspires to create biodegradable and environmentally friendly adhesives. We were inspired by bacteria, which naturally produce adhesives made from polysaccharides. Two bacteria from aquatic environments - C. crescentus and H. Baltica - harness 12 protein synthesis pathways to produce sugars anchoring them to the surfaces. We aimed to transfer the polysaccharide synthesis pathway to industrially used E. coli bacteria to produce adhesives. Our team concomitantly focused on creating a novel E. coli strain for more efficient production of adhesives.

This protein is part of the Tetrad assembly system BBa_K5246043 and operon responsible for addition of N-acetyl-D-glucosamine to N-acetyl-D-glucosamine and deacetylation of the said molecule BBa_K5246042.

Part was used in Vilnius-Lithuania iGEM 2024 project "Synhesion" https://2024.igem.wiki/vilnius-lithuania/.

This part also has a non 6xhis-tagged variant BBa_K5246012.

Usage and Biology

Caulobacter crescentus is a common freshwater gram-negative oligotrophic bacterium of the clade Caulobacterales. Its distinguishing feature is its dual lifestyle. Initially, C. crescentus daughter cells are in a “swarmer” cell phase, which has a flagellum, enabling them to perform chemotaxis. After the motile phase, they differentiate into “stalked” cells. This phase features a tubular stalk with an adhesive structure called holdfast, allowing them to adhere to surfaces and perform cell division.[1][2]

Caulobacterales synthesize a polysaccharide-based adhesin known as holdfast at one of their cell poles, enabling tight attachment to external surfaces. It is established that holdfast consists of repeating identical units composed of multiple monomers. Current literature agrees that in Caulobacter crescentus, these units form tetrads composed of glucose, an unidentified monosaccharide (either N-mannosamine uronic acid or xylose), N-acetylglucosamine, and N-glucosamine. These units are polymerized and exported to the outer membrane of the cell, where they function as anchors, securing the bacterium to a surface[3][4].

The C. crescentus holdfast is produced via a polysaccharide synthesis and export pathway similar to the group I capsular polysaccharide synthesis Wzy/Wzx-dependent pathway in Escherichia coli.

The holdfast synthesis (hfs) genes include those encoding predicted glycosyltransferases, carbohydrate modification factors, and components of a wzy-type polysaccharide assembly pathway[4][5][6][9].

HfsJ in particular most probably responsible for mannosaminuronic acid transfer to the glucose acceptor molecule.

Sequence and Features

Experimental characterization

Bioinformatic analysis

CDD analysis revealed that HfsJ is part of the WecB/TgA/CpsF glycosyltransferase family. This family catalyzes the formation of glycosidic bonds and may be involved in the biosynthesis of repeating polysaccharide units found in membrane glycolipids. It has domains very similar to E. coli WecG glycosyltransferase, which is responsible for UDP-N-acetyl-D-mannosaminuronic acid transfer. Results are supported by the protein BLAST, which showed significant similarities with the same WecG glycosyltransferase from E. coli.

DeepTMHMM analysis predicted that HfsJ is a globular protein located on the cytoplasmic side of the membrane.

AlphaFold 3 structure, with a high confidence score, shows that HfsJ is most likely a globular protein mostly made of alpha helices. A pTM score above 0.5 suggests that the predicted overall structure may closely resemble the true protein fold, while ipTM indicates the accuracy of the subunit positioning within the complex. Values higher than 0.8 represent confident, high-quality predictions (Fig.1).

Based on our findings and prior research, we propose that HfsJ is likely a globular protein responsible for transferring UDP-N-acetyl-D-mannosaminuronic acid and catalyzing the formation of a glycosidic bond. [1][2]

References

1. Toh, E., Kurtz, Harry D. and Brun, Y.V. (2008) ‘Characterization of the Caulobacter crescentus holdfast polysaccharide biosynthesis pathway reveals significant redundancy in the initiating glycosyltransferase and polymerase steps’, Journal of Bacteriology, 190(21), pp. 7219–7231. doi:10.1128/jb.01003-08.
2. Chepkwony, N.K., Berne, C. and Brun, Y.V. (2019b) ‘Comparative analysis of ionic strength tolerance between freshwater and marine Caulobacterales adhesins’, Journal of Bacteriology, 201(18). doi:10.1128/jb.00061-19.