Molecular Recognition of Methyl α-d-Mannopyranoside by Antifreeze (Glyco)Proteins

Abstract

Antifreeze proteins and glycoproteins [AF(G)Ps] have been well-known for more than three decades for their ability to inhibit the growth and recrystallization of ice through binding to specific ice crystal faces, and they show remarkable structural compatibility with specific ice crystal faces. Here, we show that the crystal growth faces of methyl α-d-mannopyranoside (MDM), a representative pyranose sugar, also show noteworthy structural compatibility with the known periodicities of AF(G)Ps. We selected fish AFGPs (AFGP8, AFGP1–5), and a beetle AFP (DAFP1) with increasing antifreeze activity as potential additives for controlling MDM crystal growth. Similar to their effects on ice growth, the AF(G)Ps can inhibit MDM crystal growth and recrystallization, and more significantly, the effectiveness for the AF(G)Ps are well correlated with their antifreeze activity. MDM crystals grown in the presence of AF(G)Ps are smaller and have better defined shapes and are of higher quality as indicated by single crystal X-ray diffraction and polarized microscopy than control crystals, but no new polymorphs of MDM were identified by single crystal X-ray diffraction, solid-state NMR, and attenuated total reflectance infrared spectroscopy. The observed changes in the average sizes of the MDM crystals can be related to the changes in the number of the MDM nuclei in the presence of the AF(G)Ps. The critical free energy change differences of the MDM nucleation in the absence and presence of the additives were calculated. These values are close to those of the ice nucleation in the presence of AF(G)Ps suggesting similar interactions are involved in the molecular recognition of MDM by the AF(G)Ps. To our knowledge this is the first report where AF(G)Ps have been used to control crystal growth of carbohydrates and on AFGPs controlling non-ice-like crystals. Our finding suggests MDM might be a possible alternative to ice for studying the detailed mechanism of AF(G)P–crystal interactions. The relationships between AF(G)Ps and carbohydrate binding proteins are also discussed. The structural compatibility between AF(G)Ps and growing crystal faces demonstrated herein adds to the repertoire of molecular recognition by AF(G)Ps, which may have potential applications in the sugar, food, pharmaceutical, and materials industries.

From ice-binding proteins to bio-inspired antifreeze materials

“…As IBPs also impact the growth 197 and morphology of crystals other than ice, 198 they may prove useful as small molecular crystal growth modifiers. 199 For example, gas hydrate inhibition by IBPs and their analogues has also become an area of considerable activity. 10 – 12 …”

Antifreeze proteins govern the precipitation of trehalose in a freezing-avoiding insect at low temperature

“…For example, the presence of AFPs in freeze-tolerant species is thought to prevent the damage caused by ice recrystallization (21). More recently, the control of the formation of crystals in addition to ice, including nucleosides and carbohydrates by AFPs, was reported in vitro (22)(23)(24), inspiring further exploration of other biological functions of AFPs, in particular, where dual functions have not been previously identified (15).…”

The Ensemble of Conformations of Antifreeze Glycoproteins (AFGP8): A Study Using Nuclear Magnetic Resonance Spectroscopy

“…A computational study supported the interaction of AFGPs with the ice surface via hydrophobic groups, but the hydrogen bonding nature of hexagonal ice (natural ice at an ambient condition) mimics that of a chair and boat conformation, which is the conformation that the disaccharides of AFGPs can take [74]. In addition, AFGPs have been shown to restructure the crystal shape of methyl α- d -mannopyranoside [75]. It seems that AFGPs tend to interact with crystals that have a structure similar to a chair and boat conformation, which the disaccharides can take.…”