Glycosylated Biofilm Proteins for Functional Biomaterials

Amyloids are fibrillar protein aggregates, dominated by β-sheets in their structure. Historically, amyloids are associated with diseases, however several functional amyloids are also identified. Biofilm proteins from microorganisms such as CsgA of Escherichia coli or TasA of Bacillus subtilis are great examples of functional amyloids with numerous applications as functional biomaterials. Due to their high mechanical strength, rigidity and resistance to harsh environmental conditions, amyloids emerged as outstanding biomaterials.

Protein glycosylation is one of the most common post-translational modifications, which is classified into two groups as N-linked and O- linked glycosylation. Protein glycosylation is firstly identified in eukaryotic cells; however, bacterial glycosylation is also discovered in the past twenty years, especially associated with pathogenicity. The first identified prokaryotic species that possess N-linked glycosylation is Campylobacter jejuni, a pathogenic bacterium that causesgastroenteritis. The pgl glycosylation pathway from C. jejuni is transferred to E. coli and successful protein glycosylation is achieved. Glycosylation is crucial for adhesiveness of proteins. Therefore, glycosylation can be utilized as a practical tool to alter adhesive properties of target proteins for protein-based biomaterial applications.

Given the fact that amyloid-like TasA fibrils are utilized in biomaterial research, we hypothesized that adhesiveness of TasA fibrils may be enhanced via glycosylation. To that end, TasA is engineered to have DQNAT glycosylation motif at the C terminal and expressed it in E. coli containing pgl circuit. Adhesive and viscoelastic properties of TasA fibrils are examined on solid surfaces. We showed that glycosylation can indeed enhance adhesive properties of TasA fibrils without disrupting fibrillization. Our results demonstrated that de novo glycosylation can be used as a tool to produce biomaterials with superior adhesive performance [1]. Supported by TUBITAK 216M127.

[1] E. Sahin Kehribar, M. E. Isilak, E. U. Bozkurt, J. Adamcik, R. Mezzenga, U. O. S. Seker, Biomater. Sci. 2021, DOI 10.1039/D0BM02192J.