About The Antifeeze Protein?

1) How does this protein keep the arctic cod and the antarctic notothenioid from freezing?

2)Do any other animals have similar adaptation?

1 Answer

  • 1 decade ago
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    Antarctic cod--and many of their smaller cousins--are the subjects of ongoing research by the husband-and-wife team of Art DeVries and Chris Cheng-DeVries, both scientists at the University of Illinois.

    Art DeVries, a McMurdo institution himself, has been traveling to the Ice for more than three decades, examining the mechanism by which Antarctic fish avoid freezing.

    Swimming in a sea that is below 32 F, the cold-blooded creatures run the constant risk of ice crystals forming in their blood. Once a single crystal enters, others can nucleate around it, precipitating a potentially deadly chain reaction.

    While subsurface seawater stays liquid due to its high salt content, fluids in fish don't share the same advantage. What they do have, as Art DeVries discovered years ago, is antifreeze.

    Fish antifreeze isn't like the antifreeze in your car, explained Cheng-DeVries. It doesn't lower the actual freezing point of the fish's blood. Instead, she said, "it inhibits the preferred direction of growth of the ice crystals."

    Ice crystals, she explained, are laid out like flat hexagons. They expand when other hexagons interlock on their six exposed sides, forming a pattern like that on a soccer ball.

    But in the supercooled waters of the Antarctic, fish in the family notothenioid--which includes the giant mawsoni--generate a substance called antifreeze glycoprotein, or AFGP. AFGP circulates in their blood and beats any ice crystals to the punch, surrounding them, binding to their sides and thus arresting crystal growth.

    This discovery has taken the DeVries' research in a range of different directions.

    According to Cheng-DeVries, they're still studying how AFGP binds to ice--an odd act in the molecular world. "Most proteins interact with other proteins," she said. "These guys interact with ice."

    In a completely different vein, the researchers are also conducting genetic studies of AFGP to help determine when Antarctica began the dramatic cooling trend that converted it from a mild environment to the ice continent of today.

    According to Cheng-DeVries, notothenioids evolved AFGP as a response to that climatic shift, while non-adaptive species died out. By calculating when AFGP arose, the timing of the continental cold snap can be better determined.

    A third avenue of inquiry involves the formation of AFGP in embryos. Because the fish spawn and fertilize their eggs externally, the eggs must develop antifreeze early on, to protect them from their frigid surroundings.

    According to Cheng-DeVries, that mystery will likely bring the research team back to McMurdo Sound during Winfly next season, so they can follow the fish eggs throughout their developmental cycle.

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