a) BioConjugation through enzyme (sortase) based linking technology:

A new and interesting application of oligo-Gly is its use in Sortase linking technology, where oligo-Gly binds as free N- Terminus to the recognition motif (LPXTG) of the C-terminus of a protein of interest. The transpeptidase activity of sortase is used by structural biologists to produce fusion proteins in vitro. In the presence of sortase, the two peptides are covalently linked through a native peptide bond.

b) Linker through Click reaction or chemical amid bond formation:

The azide function is widely used for coupling to alkyne-containing fragments via the renowned Click reaction.

Besides that, oligo-Gly has been used as linker to combine different subunits of dimeric or oligomeric proteins or to create artificial multi-domain proteins. By modification into Gly-Gly-Gly-Ser motifs, high solubility can be achieved. Most of the linkers are rigid and function to prohibit unwanted interactions between the discrete domains. However, Gly-rich linkers are flexible, connecting various domains in a single protein without interfering with the function of each domain. The flexibility of oligo-Gly is much higher than for any other amino acid combination due to large areas of allowed Phi/Psi-angle combinations in the Ramachandran plot. This enables formation of unusual structure elements like turns, breaks of helices and sheets and many others.

Other applications:

Oligo-Gly designed in a star-like fashion, so-called tri- and tetraantennary molecules, were found to form highly ordered supramers in aqueous medium.

Polyglycine fragments containing up to 7 glycines are reported to bind to surfaces and have potential application in nanotechnology constructs: Gly7-NHCH2-fragment containing peptides bind on mica surface in aqueous solution. Furthermore, oligo-glycine has been used as a flexible linker between DNA binding domains. A variation of glycine and alanine containing linkers were used in libraries of single-chain Arc repressor in order to tune flexibility and stability.

Proteins and DNA have been proven usefully being fused by Gly-rich linkers.

Polyglycine units - as natural peptide type linkers - were employed to connect the original N- and C- termini of a circularly permuted constructs of Escherichia coli dihydrofolate reductase (DHFR).

Referenzen

• DNA-Bending Finger: Artificial Design of 6-Zinc Finger Peptides with Polyglycine Linker and Induction of DNA Bending; M. Imanishi, Y. Hori, M. Nagaoka and Y. Sugiura; Biochemistry 2000; 39: 4383-4390. doi:10.1021/bi992989b
• Biantennary oligoglycines and glyco-oligoglycines self-associating in aqueous medium; S. V. Tsygankova, A. A. Chinarev, A. B. Tuzikov, N. Severin, A. A. Kalachev, J. P. Rabe, A. S. Gambaryan and N. V. Bovin; Beilstein Journal of Organic Chemistry 2014; 10: 1372-1382. doi:10.3762/bjoc.10.140
• Assembly of Oligoglycine Layers on Mica Surface; S. V. Tsygankova, A. A. Chinarev, A. B. Tuzikov, I. S. Zaitsev, N. Severin, A. A. Kalachev, J. P. Rabe and N. V. Bovin; Journal of Biomaterials and Nanobiotechnology 2011; 2: 91-97. doi:10.4236/jbnb.2011.21012
• Linkers in the structural biology of protein–protein interactions; V. P. Reddy Chichili, V. Kumar and J. Sivaraman; Protein Science 2013; 22: 153-167. doi:10.1002/pro.2206
• Effects of the length of a glycine linker connecting the N-and C-termini of a circularly permuted dihydrofolate reductase; M. Iwakura and T. Nakamura; Protein Engineering 1998; 11: 707-713. doi:10.1093/protein/11.8.707
• Optimizing the stability of single-chain proteins by linker length and composition mutagenesis; C. R. Robinson and R. T. Sauer; Proc Natl Acad Sci U S A 1998; 95: 5929-5934.
• Sortase-Mediated Protein Ligation: A New Method for Protein Engineering; H. Mao, S. A. Hart, A. Schink and B. A. Pollok; J Am Chem Soc 2004; 126: 2670-2671. doi:10.1021/ja039915e
• Sortase-Tag Expressed Protein Ligation: Combining Protein Purification and Site-Specific Bioconjugation into a Single Step; R. Warden-Rothman, I. Caturegli, V. Popik and A. Tsourkas; Anal Chem 2013; 85: 11090-11097. doi:10.1021/ac402871k