Nav: Home

How antifreeze proteins stop ice cold

July 09, 2018

How do insects survive harsh northern winters?  Unlike mammals, they don't have thick coats of fur to keep warm.  But they do have antifreeze. Antifreeze proteins (AFPs) prevent ice from forming and spreading inside their bodies.

The existence of these AFPs has been known for decades, but the mechanisms governing this unique survival technique have proven difficult to determine.  A new study published in the Proceedings of the National Academy of Sciences by researchers at the University of Utah and University of California, San Diego shows how AFPs function while also providing a direction for future research.

Recognizing ice before it's ice

AFPs prevent water from freezing by surrounding and quickly binding to small ice crystals, where water has already managed to order itself into an ice lattice.  Left unattended, these crystals would otherwise act as seeds and continue to spread their ordering to neighboring water molecules.  The prevailing hypothesis for how AFPs stop this mechanism has been the preordering of an ice-like layer of water near the site of the protein that binds to the ice surface.  However, primarily due to the difficulty of isolating this small region in experiments from the surrounding ice and water, this had yet to be proven, says U. chemistry professor Valeria Molinero.

Focusing on the AFP of the mealworm beetle, Tenebrio molitor(TmAFP), the study aimed to test this hypothesis through theoretical methods at different resolutions of space and time. Molinero specializes in simulating ice at larger scales and applied this expertise to a system with TmAFP in water approaching an ice surface. With this setup, she and her doctoral student Arpa Hudait observed the protein slowly tumbling above the ice surface. They discovered that to latch on to the ice, all TmAFP requires is to be parallel to the surface.

Importantly, however, this anchoring did not require any prior ordering of the water into an ice-like structure. "The slow movement of the protein to be parallel to the ice surface is followed immediately by a fast reorientation of the nearby water to bind the protein to the ice," Hudait says. In insects like the mealworm beetle, this binding of many AFPs to developing ice crystals prevents further crystallization of ice in their bodies.

How to watch it happening

But Molinero's methods lacked the accuracy necessary to create spectroscopic predictions of what the binding event would look like to spectroscopic instruments.  With his highly accurate water model, Francesco Paesani of UCSD, and his postdoctoral researcher, Daniel Moberg, collaborated with Molinero and her team to calculate both the infrared and Raman spectra with unprecedented accuracy. "Simulations have the advantage of being able to isolate any desired region, though this is only useful if the underlying theory is accurate enough," explains Paesani.

This was the first study to have determined the signal from only the structures anchoring the protein to the ice surface, called clathrates.  "Our results show that infrared spectroscopy is unlikely to provide much information on the anchored clathrate structure," says Moberg. "Raman spectroscopy, however, should show differences if experimentalists can isolate the signal from the binding site or anchored clathrate."

The findings can lend insight to studies of ice nucleating proteins in the atmosphere, which perform the opposite task and play a role in forming ice crystals in clouds. "We predict that preordering could emerge on the large surfaces of aggregated ice-nucleating proteins, where it may serve the opposite role of assisting with ice nucleation in clouds," Molinero says.

There's widespread interest in learning to mimic the antifreeze mechanism of AFPs, she adds, with applications from organ preservation to plane de-icing. "There's a big potential market for antifreeze based on the same mechanism - but if you don't understand the mechanism it's difficult to define and optimize molecules."
-end-
This study was funded by the National Science Foundation. This release is adapted from text provided by Daniel Moberg.

University of Utah

Related Protein Articles:

Hi-res view of protein complex shows how it breaks up protein tangles
A new, high-resolution view of the structure of Hsp104 (heat shock protein 104), a natural yeast protein nanomachine with six subunits, may show news ways to dismantle harmful protein clumps in disease.
Breaking the protein-DNA bond
A new Northwestern University study finds that unbound proteins in a cell break up protein-DNA bonds as they compete for the single-binding site.
FASEB Science Research Conference: Protein Kinases and Protein Phosphorylation
This conference focuses on the biology of protein kinases and phosphorylation signaling.
Largest resource of human protein-protein interactions can help interpret genomic data
An international research team has developed the largest database of protein-to-protein interaction networks, a resource that can illuminate how numerous disease-associated genes contribute to disease development and progression.
STAT2: Much more than an antiviral protein
A protein known for guarding against viral infections leads a double life, new research shows, and can interfere with cell growth and the defense against parasites.
A protein makes the difference
It is well-established knowledge that blood vessels foster the growth of tumors.
Nuclear protein causes neuroblastoma to become more aggressive
Aggressive forms of neuroblastoma contain a specific protein in their cells' nuclei that is not found in the nuclei of more benign forms of the cancer, and the discovery, made through research from the University of Rochester Medical Center, could lead to new forms of targeted therapy.
How a protein could become the next big sweetener
High-fructose corn syrup and sugar are on the outs with calorie-wary consumers.
High animal protein intake associated with higher, plant protein with lower mortality rate
The largest study to examine the effects of different sources of dietary protein found that a high intake of proteins from animal sources -- particularly processed and unprocessed red meats -- was associated with a higher mortality rate, while a high intake of protein from plant sources was associated with a lower risk of death.
Protein in, ammonia out
A recent study has compiled and analyzed data from 25 previous studies.

Related Protein Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...