Glycosylation of a Nonfibrillizing Appendage Alters the Self-Assembly Pathway of a Synthetic β-Sheet Fibrillizing Peptide

Abstract

Owing to their biocompatibility and biodegradability, short synthetic peptides that self-assemble into elongated β-sheet fibers (i.e., peptide nanofibers) are widely used to create biomaterials for diverse medical and biotechnology applications. Glycosylation, which is a common protein post-translational modification, is gaining interest for creating peptide nanofibers that can mimic the function of natural carbohydrate-modified proteins. Recent reports have shown that glycosylation can disrupt the fibrillization of natural amyloid-forming peptides. Here, using transmission electron microscopy, fluorescence microscopy, and thioflavin T spectroscopy, we show that glycosylation at a site external to the fibrillization domain can alter the self-assembly pathway of a synthetic fibrillizing peptide, NSGSGQQK­FQFQFEQQ (NQ11). Specifically, an NQ11 variant modified with N-linked N-acetylglucosamine, N­(GlcNAc)­SGSG-Q11 (GQ11), formed β-sheet nanofibers more slowly than NQ11 in deionized water (pH 5.8), which correlated to the tendency of GQ11 to form a combination of short fibrils and nonfibrillar aggregates, whereas NQ11 formed extended nanofibers. Acidic phosphate buffer slowed the rate of GQ11 fibrillization and altered the morphology of the structures formed yet had no effect on NQ11 fibrillization rate or morphology. The buffer ionic strength had no effect on the fibrillization rate of either peptide, while the diphosphate anion had a similar effect on the rate of fibrillization of both peptides. Collectively, these data demonstrate that a glycan moiety located external to the β-sheet fibrillizing domain can alter the pH-dependent self-assembly pathway of a synthetic peptide, leading to significant changes in the fibril mass and morphology of the structures formed. These observations add to the understanding of the effect of glycosylation on peptide self-assembly and should guide future efforts to develop biomaterials from synthetic β-sheet fibrillizing glycopeptides.

Parallel β-Sheet Structure and Structural Heterogeneity Detected within Q11 Self-Assembling Peptide Nanofibers

“…We prepared Q11 peptides for NMR measurements at 10 mg/mL (or 6.6 mM) peptide concentration in water then left the samples at 4 °C overnight following established protocols for the self-assembly of Q11. ,− We then diluted the solutions to 1 mg/mL peptide concentration using 1x PBS. To pack the samples into Bruker 3.2 mm NMR rotors (sample holders), we ultracentrifuged samples at 150,000 RCF and 4 °C for 30 min using a custom widget in Ultraclear tubes and a SW-41 swinging bucket rotor on a Beckman Optima XPN-100 Centrifuge.…”