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PubMed · 1730239

Protein interaction with ice.

C L Hew·D S Yang
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Abstract

Many organisms have evolved novel mechanisms to minimize freezing injury due to extracellular ice formation. This article reviews our present knowledge on the structure and mode of action of two types of proteins capable of ice interaction. The antifreeze proteins inhibit ice crystal formation and alter ice growth habits. The ice nucleation proteins, on the other hand, provide a proper template to stimulate ice growth. The potential applications of these proteins in different industries are discussed.

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Antifreeze ProteinsBacterial Outer Membrane ProteinsBacterial ProteinsBinding SitesCrystallizationFreezingGlycoproteinsIceProtein ConformationJournal ArticleResearch Support, Non-U.S. Gov'tReview

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C L Hew, D S Yang. 1992-01-15. Protein interaction with ice.. https://doi.org/10.1111/j.1432-1033.1992.tb19824.x

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PubMed2006

Insight into the binding of antifreeze proteins to ice surfaces via 13C spin lattice relaxation solid-state NMR.

The primary sequences of type I antifreeze proteins (AFPs) are Ala rich and contain three 11-residue repeat units beginning with threonine residues. Their secondary structures consist of alpha-helices. Previous activity study of side-chain mutated AFPs suggests that the ice-binding side of type I AFPs comprises the Thr side chains and the conserved i + 4 and i + 8 Ala residues, where i indicates the positions of the Thrs. To find structural evidence for the AFP's ice-binding side, a variable-temperature dependent (13)C spin lattice relaxation solid-state NMR experiment was carried out for two Ala side chain (13)C labeled HPLC6 isoforms of the type I AFPs each frozen in H(2)O and D(2)O, respectively. The first one was labeled on the equivalent 17th and 21st Ala side chains (i + 4, 8), and the second one on the equivalent 8th, 19th, and 30th Ala side chains (i + 6). The two kinds of labels are on the opposite sides of the alpha-helical AFP. A model of Ala methyl group rotation/three-site rotational jump combined with water molecular reorientation was tested to probe the interactions of the methyl groups with the proximate water molecules. Analysis of the T(1) data shows that there could be 10 water molecules closely capping an i + 4 or an i + 8 methyl group within the range of van der Waals interaction, whereas the surrounding water molecules to the i + 6 methyl groups could be looser. This study suggests that the side of the alpha-helical AFP comprising the i + 4 and i + 8 Ala methyl groups could interact with the ice surface in the ice/water interface.

Antifreeze Proteins↗
PubMed2006

Aggregation of antifreeze glycoprotein fraction 8 and its effect on antifreeze activity.

Antifreeze glycoproteins (AFGPs) have many potential applications ranging from the cryopreservation and hypothermic storage of tissues and organs to the preservation of various frozen food products. Since supplying native AFGP for these applications is a labor-intensive and costly process, the rational design and synthesis of functional AFGP analogues is a very attractive alternative. While structure-function studies have implicated specific structural motifs as essential for antifreeze activity in AFGP, the relationship between solution conformation and antifreeze activity is poorly understood. Toward this end, we have analyzed AFGP8 in aqueous solutions using dynamic light scattering (DLS) and circular dichroism (CD). Our results indicate that AFGP8 forms discrete aggregates in solution. These aggregates are predominantly composed of dimers that form at solution concentrations greater than 20 mM. CD spectroscopy indicates that the preferred solution conformation of AFGP8 is consistent with that of random coil. However, significant beta-sheet and alpha-helix character is observed in more concentrated solutions, indicating that these glycopeptides are highly flexible in solution. Aggregation appears to have a minimal effect on the overall solution conformation. Thermal hysteresis (TH) activity of the aggregated solutions is much higher than that of less concentrated solutions that do not form aggregates. While cooperative functioning between lower and higher molecular weight AFGPs has been reported, this is the first instance where cooperative functioning in lower molecular weight AFGPs has been observed.

Antifreeze Proteins↗