The Effect of Oligomerization on A Solid-Binding Peptide Binding to Silica-Based Materials

Rachit Bansal; Zehra Elgundi; Sophia C Goodchild; Andrew Care; Megan S Lord; Alison Rodger; Anwar Sunna

doi:10.3390/nano10061070

The Effect of Oligomerization on A Solid-Binding Peptide Binding to Silica-Based Materials

Nanomaterials (Basel). 2020 May 30;10(6):1070. doi: 10.3390/nano10061070.

Authors

Rachit Bansal^{1

2}, Zehra Elgundi³, Sophia C Goodchild¹, Andrew Care^{1

2}, Megan S Lord³, Alison Rodger¹, Anwar Sunna^{1

2

4}

Affiliations

¹ Department of Molecular Sciences, Macquarie University, Sydney, NSW 2109, Australia.
² ARC Centre of Excellence for Nanoscale Biophotonics, Macquarie University, Sydney, NSW 2109, Australia.
³ Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
⁴ Biomolecular Discovery Research Centre, Macquarie University, Sydney, NSW 2109, Australia.

Abstract

The bifunctional linker-protein G (LPG) fusion protein comprises a peptide (linker) sequence and a truncated form of Streptococcus strain G148 protein G (protein G). The linker represents a multimeric solid-binding peptide (SBP) comprising 4 × 21-amino acid sequence repeats that display high binding affinity towards silica-based materials. In this study, several truncated derivatives were investigated to determine the effect of the SBP oligomerization on the silica binding function of LPG (for the sake of clarity, LPG will be referred from here on as 4 × LPG). Various biophysical characterization techniques were used to quantify and compare the truncated derivatives against 4 × LPG and protein G without linker (PG). The derivative containing two sequence repeats (2 × LPG) showed minimal binding to silica, while the truncated derivative with only a single sequence (1 × LPG) displayed no binding. The derivative containing three sequence repeats (3 × LPG) was able to bind to silica with a binding affinity of K_D = 53.23 ± 4.5 nM, which is 1.5 times lower than that obtained for 4 × LPG under similar experimental conditions. Circular dichroism (CD) spectroscopy and fluorescence spectroscopy studies indicated that the SBP degree of oligomerization has only a small effect on the secondary structure (the linker unravels the beginning of the protein G sequence) and chemical stability of the parent protein G. However, based on quartz crystal microbalance with dissipation monitoring (QCM-D), oligomerization is an important parameter for a strong and stable binding to silica. The replacement of three sequence repeats by a (GGGGS)₁₂ glycine-rich spacer indicated that the overall length rather than the SBP oligomerization mediated the effective binding to silica.

Keywords: linker-protein G; oligomerization; quartz crystal microbalance with dissipation monitoring (QCM-D); silica-based materials; silica-binding peptide; solid-binding peptide (SBP).