Inhibition of bacterial ice nucleators by fish antifreeze glycoproteins

Abstract

Certain bacteria promote the formation of ice in super-cooled water by means of ice nucleators which contain a unique protein associated with the cell membrane. Ice nucleators in general are believed to act by mimicking the structure of an ice crystal surface, thus imposing an ice-like arrangement on the water molecules in contact with the nucleating surface and lowering the energy necessary for the initiation of ice formation. Quantitative investigation of the bacterial ice-nucleating process has recently been made possible by the discovery of certain bacteria that shed stable membrane vesicles with ice nucleating activity. The opposite effect, inhibition of ice formation, has been described for a group of glycoproteins found in different fish and insect species. This group of substances, termed antifreeze glycoproteins (AFGPs), promotes the supercooling of water with no appreciable effect on the equilibrium freezing point or melting temperature. Substantial evidence now indicates that AFGPs act by binding to a growing ice crystal and slowing crystal growth. As the ice-nucleating protein surface is believed to have a structure similar to an embryonic ice crystal, AFGPs might be predicted to interact directly with a bacterial ice-nucleating site. We report here that AFGPs from the antarctic fish Dissostichus mawsoni inhibit the ice-nucleating activity of membrane vesicles from the bacterium Erwinia herbicola. The inhibition effect shows saturation at high concentration of AFGP and conforms to a simple binding reaction between the AFGP and the nucleation centre.

Anti-ice nucleation activity in xylem extracts from trees that contain deep supercooling xylem parenchyma cells

“…We confirmed this by using emulsified micro-water droplets with diameters less than 10 µm [1]. Antifreeze glycoproteins from fish also have the same effects as those of crude xylem extracts, showing the presence of anti-ice nucleation activity toward heterogeneous ice nucleators [34,45] but absence of activity toward homogeneous ice nucleation [13,45].…”

“…There are some previous reports about anti-ice nucleation substances that enhance supercooling of water as listed in Table 1. Antifreeze proteins from insects [11], antifreeze proteins and antifreeze glycoproteins from fish [20,34,45], anti-nucleating proteins from bacteria [29], and polysaccharides from bacteria [49] exhibit anti-ice nucleation activity toward water droplets. As substances originating from plants, hinokitiol from the leaves of Taiwan yellow cypress [28] and eugenol from clove reduce ice nucleation activity of water [30].…”

Type I Antifreeze Proteins Enhance Ice Nucleation above Certain Concentrations

“…Parody-Morreale et al (4) reported that AFGP molecules from the Antarctic notothenioid Dissostichus mawsoni inhibit the ice-nucleating activity of membrane vesicles from the bacterium Erwinia hebicola. Using a drop-freezing assay to characterize the populations of ice nucleators, they reported saturation at high AFGP concentrations and concluded that AFGPs bind to and inhibit ice-nucleating proteins.…”

Interaction of ice binding proteins with ice, water and ions

“…13,27 Potential ice nucleators are removed from the body or inactivated by IBPs. 12,[28][29][30] While ice-formation is lethal for freeze-avoiding organisms such as fish and most insects, freeze-tolerant plants and insects allow controlled freezing of extracellular spaces during the winter season. 13,31 Because intracellular ice would also be lethal for freeze-tolerant species, they use INPs to prevent extensive supercooling and initiate extracellular ice nucleation at relatively low supercooling [ Fig.…”