Synthesis of peptides and glycopeptides with polyproline II helical topology as potential antifreeze molecules

Abstract

A library of peptides and glycopeptides containing (4R)-hydroxy-L-proline (Hyp) residues were designed with a view to providing stable polyproline II (PPII) helical molecules with antifreeze activity. A library of dodecapeptides containing contiguous Hyp residues or an Ala-Hyp-Ala tripeptide repeat sequence were synthesized with and without α-O-linked N-acetylgalactosamine and α-O-linked galactose-β-(1→3)-N-acetylgalactosamine appended to the peptide backbone. All (glyco)peptides possessed PPII helical secondary structure with some showing significant thermal stability. The majority of the (glyco)peptides did not exhibit thermal hysteresis (TH) activity and were not capable of modifying the morphology of ice crystals. However, an unglycosylated Ala-Hyp-Ala repeat peptide did show significant TH and ice crystal re-shaping activity suggesting that it was capable of binding to the surface of ice. All (glyco)peptides synthesized displayed some ice recrystallization inhibition (IRI) activity with unglycosylated peptides containing the Ala-Hyp-Ala motif exhibiting the most potent inhibitory activity. Interestingly, although glycosylation is critical to the activity of native antifreeze glycoproteins (AFGPs) that possess an Ala-Thr-Ala tripeptide repeat, this same structural modification is detrimental to the antifreeze activity of the Ala-Hyp-Ala repeat peptides studied here.

OGlcNAcylation and Phosphorylation Have Similar Structural Effects in α-Helices: Post-Translational Modifications as Inducible Start and Stop Signals in α-Helices, with Greater Structural Effects on Threonine Modification

“…Indeed, in a limited number of examples, including antifreeze proteins and the prion protein, dramatic structural differences were observed between modification of Ser/Thr residues with α anomers versus β anomers of sugars. 42,168,169 Data to date suggest that β anomers exhibit substantial steric effects near the backbone, similar to β-branched and aromatic amino acids, whereas α anomers are more compatible with compact protein conformations.…”

Toward structure prediction of cyclic peptides

“…Furthermore, owing to their macrocyclic character, small modifications to cyclic peptides often cause massive conformational alterations. [17][18][19][20][21] Most of these methods are based on the implicit solvent model. 7,16 In the past years, several methods have been proposed to predict the three-dimensional structure of cyclic peptides using computer simulations.…”

Gold Nanoparticle Aggregation as a Probe of Antifreeze (Glyco) Protein-Inspired Ice Recrystallization Inhibition and Identification of New IRI Active Macromolecules

“…Therefore, the development of new IRI-specific molecules/macromolecules has been pursued. Ben et al have reported that simplified glycopeptides and glycolipids have potent IRI and can enhance cryopreservation 11 12 13 . Gibson and co-workers have shown that synthetic polymers can mimic AF(G)Ps function and shown this to enhance red blood cell cryopreservation 14 15 16 .…”