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Biological Strategies in Nanobiocatalyst Assembly
Published in Grunwald Peter, Biocatalysis and Nanotechnology, 2017
Ian Dominic F. Tabañag, Shen-Long Tsai
Sortase A is an enzyme used by Gram-positive bacteria to anchor surface proteins to the cell wall through a condensation reaction between a C-terminal LPXTG (where X is any amino acid) tag on the former and a polyglycine bridge in the latter such that the enzyme cleaves the LPXTG sequence at the amide bond between the threonine and the glycine to form an acyl-protein (transpeptidase reaction) complex (Ton-That et al., 1997). The LPXTG recognition motif of Sortase A in the enzymatic ligation is highly selective which makes it attractive for protein modification. It has been demonstrated that Sortase A from Staphylococcus aureus provides a robust and mild approach for selective enzyme-mediated immobilization of proteins onto solid surfaces (Parthasarathy et al., 2007; Chan et al., 2007; Clow et al., 2008).
Kode Technology – a universal cell surface glycan modification technology
Published in Journal of the Royal Society of New Zealand, 2019
Stephen M. Henry, Nicolai V. Bovin
Synthesis of FSLs is carried out in a block-wise fashion (Figure 4). First the individual parts (Function, Spacer and Lipid) are chemically synthesised, each with appropriate chemical conjugation handles (Korchagina et al. 2012). Next the spacer and lipid are conjugated together, resulting in a Spacer-Lipid precursor with one of selection of conjugation handles selected to be optimal for reactivity with the functional head group. Typically, glycans are synthesised as aminopropyl glycosides (Solís et al. 2015), or if the glycan is isolated from natural sources as free oligosaccharide, it is modified with a glycylamido linker (Tuzikov et al. 2000; Solís et al. 2015). Glycans are reacted with Spacer-Lipids with an activated carboxyl group (usually N-hydroxysuccinimide); maleimide is used for interacting with cysteine handles on glycopeptides (Figure 4). Sometimes an alternative strategy is used where a pre-synthesised Function-Spacer is conjugated to a Lipid (in contrast to the Spacer-Lipid being conjugated to a Function); the choice of strategy is due to several factors but primarily the simplicity of isolation of the final FSL product from the reaction mixture. Because Kode Technology is inherently flexible a large range of different additional covalent chemistries can be utilised, including click chemistry (Fink and Seibel 2018). Furthermore, the functional head can be designed to secondarily capture other functional heads to allow post FSL modification of a cell (kodecyte) to capture of larger molecules at the cell surface. For example, primary FSL constructs containing chelators, enzyme substrates (like sortase), alkyne or azido handles (for click chemistry) and biotin (Dube and Bertozzi 2003; Henry et al. 2018a) have all been demonstrated to attach larger molecules to the surface of cells (kodecytes).