Part:BBa_K5246032
HB 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 the addition of N-acetyl-D-glucosamine and deacetylation of the former 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 his-tagged variant BBa_K5246022.
Biology and usage
Biology
Hirschia baltica is a common marine of the clade Caulobacterales. Its distinguishing feature is its dual lifestyle. Initially, H. baltica 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 a 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 H. baltica 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].
HfsG in particular is responsible for N-acetyl-D-glucosamine transfer to the acceptor molecule.
HfsJ
"Gene HfsJ from Hirschia baltica encodes a protein of 260 amino acids. HfsJ is one of the glycosyltransferases involved in holdfast synthesis pathway and is structurally very similar to glycosyltransferases that transfer UDP-N-acetyl-D-mannosaminuronic acid. Ir belongs to the WecB/TagA/CpsF family of glycosyltransferases that catalyze the formation of glycosidic bonds and may be involved in the biosynthesis of repeating polysaccharide units found in membrane glycolipids. It is predicted that this is an intracellular protein."
Usage
Proteins of the holdfast synthesis system assemble a short chain of sugar monomers in a specific sequence on a lipid carrier - a glycolipid.
Glycolipids are predominantly located on the extracellular surface of eukaryotic cell membranes and are responsible for various functions such as receptors for viruses and other pathogens, allowing them to enter a specific host cell that has unique glycolipid markers. This feature can let us use said glycolipids as labels for a precise and targeted liposome distribution throughout the body, delivering anything from cancer drugs to gene editing systems directly to the target cells.
To create a liposome labeling system, we had to select specific proteins that could be utilized for this purpose. Following bioinformatics analysis using the Conserved Domain Database, Protein BLAST, DeepTMHMM, and AlphaFold 3, we identified five proteins of interest from each strain: HfsG, HfsH, HfsJ, HfsK, and HfsL.
To utilize these enzymes, it was essential to develop a suitable purification strategy. For efficient cloning, we chose Golden Gate assembly. For efficient purification, we selected immobilized ion affinity chromatography (IMAC) as our purification method, based on recommendations from one of the few available papers where C. crescentus proteins were expressed and purified from E. coli. We opted for conventional 6x histidine tags (his-tag) to facilitate straightforward purification. It was crucial to determine the appropriate terminus for 6xHis-tag insertion to avoid disrupting the protein conformation and lessening purification efficiency.
Sequence and Features
- 10INCOMPATIBLE WITH RFC[10]Illegal PstI site found at 188
- 12INCOMPATIBLE WITH RFC[12]Illegal PstI site found at 188
- 21INCOMPATIBLE WITH RFC[21]Illegal BglII site found at 622
- 23INCOMPATIBLE WITH RFC[23]Illegal PstI site found at 188
- 25INCOMPATIBLE WITH RFC[25]Illegal PstI site found at 188
- 1000COMPATIBLE WITH RFC[1000]
Experimental characterization
Protein expression
Hirschia baltica
We chose the BL21(DE3) strain for adjustable and efficient expression of target proteins since the system's proteins were best expressed in this strain. Given the lack of time, we went with conditions optimized beforehand in earlier experiments for the whole pathway expression: temperature of 37°C, induction with 0.5 mM IPTG concentration, and expression for 3 hours.
After SDS-PAGE gel analysis, we concluded that we successfully expressed HfsG, HfsH, HfsK, and HfsL proteins from H. baltica. Unfortunately, HfsJ was not properly expressed and need more optimization
HfsJ unfortunately is not visible on the gel (Fig. 1).
Table 1. H. baltica protein sizes in kDa
| Protein Name | Size (kDa) |
|---|---|
| HfsG | 37 |
| HfsH | 29 |
| HfsJ | 41 |
| HfsK | 28 |
| HfsL | 36 |
References
1. Hendrickson, H., & Lawrence, J. G. (2000). Mutational bias suggests that replication termination occurs near the dif site, not at Ter sites. FEMS Microbiology Reviews, 24(2), 177–183. https://doi.org/10.1111/j.1574-6976.2000.tb00539.x
2. Andrews, S. C., Robinson, A. K., & Rodríguez-Quiñones, F. (2004). Bacterial iron homeostasis. Journal of Bacteriology, 186(5), 1438–1447. https://doi.org/10.1128/jb.186.5.1438-1447.2004
3.Rabah, A., & Hanchi, S. (2023). Experimental and modeling study of the rheological and thermophysical properties of molybdenum disulfide-based nanofluids. Journal of Molecular Liquids, 384, 123335. https://doi.org/10.1016/j.molliq.2023.123335
4. Boutte, C. C., & Crosson, S. (2009). Bacterial lifestyle shapes stringent response activation. Journal of Bacteriology, 191(9), 2904-2912. https://doi.org/10.1128/jb.01003-08
5. Mackie, J., Liu, Y. C., & DiBartolo, G. (2019). The C-terminal region of the Caulobacter crescentus CtrA protein inhibits stalk synthesis during the G1-to-S transition. mBio, 10(2), e02273-18. https://doi.org/10.1128/mbio.02273-18
6.Thanbichler, M., & Shapiro, L. (2003). MipZ, a spatial regulator coordinating chromosome segregation with cell division in Caulobacter. Journal of Bacteriology, 185(4), 1432-1442. https://doi.org/10.1128/jb.185.4.1432-1442.2003
7. Hershey, D.M., Fiebig, A. and Crosson, S. (2019) ‘A genome-wide analysis of adhesion in Caulobacter crescentus identifies new regulatory and biosynthetic components for holdfast assembly’, mBio, 10(1). doi:10.1128/mbio.02273-18.
8. Chepkwony, N.K., Hardy, G.G. and Brun, Y.V. (2022) ‘HFAE is a component of the holdfast anchor complex that tethers the holdfast adhesin to the cell envelope’, Journal of Bacteriology, 204(11). doi:10.1128/jb.00273-22.
9. Chepkwony, N.K., Berne, C. and Brun, Y.V. (2019) ‘Comparative analysis of ionic strength tolerance between freshwater and marine Caulobacterales adhesins’, Journal of Bacteriology, 201(18). doi:10.1128/jb.00061-19.
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.
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