Protein Compass Might Explain How Animals Detect Magnetic Fields

And could someday help combat disease in humans

Researchers found the protein complex on pigeon retinas

Alan D. Wilson via Wikimedia Commons

How do birds migrate thousands of miles, and how does a burrowing mole rat know which way is up? The answer lies in the animals’ ability to detect magnetic fields--an idea that was long controversial but is now well established. But so far the mechanism that gives animals (and possibly humans) this capability isn’t well understood. Some researchers have suspected that certain types of chemicals might be involved, but they weren’t sure which ones or how to find them.

Now, a team of Chinese researchers has discovered a protein complex—a "chemical compass," as the scientists call it—that lines up with magnetic fields, according to a study published today in Nature Materials. The complex might hold the key to animals' magnetic-sensing power.

The researchers set out in search of the chemical compass, and previous studies had suggested that cryptochromes--proteins that are light-sensitive and known to regulate the circadian rhythm of many plants and animals--might be involved in sensing magnetic fields. Some fruit flies can sense magnetic fields, so the team scanned the fly's entire genome, searching for iron-based proteins that might bind with the flies' cryptochrome. They whittled the options down to 14 proteins. After testing these in the lab, they found only one that formed a stable complex with the cryptochrome, which they named magnetoreceptor protein (MagR).

The scientists then scanned the genomes of 13 other species known to have magnetic-sensing abilities, and found iterations of the same genetic blueprint for MagR in each.

Armed with digital models of the proteins, the researchers created antibodies that, should MagR be present in a tissue, would cause a reaction. They tested the antibodies on the retinas of pigeons, which are thought to be able to process magnetic fields visually, and found that they did react, suggesting that the MagR complex is present in pigeon eyes.

Finally, when researchers exposed MagR complexes to magnetic fields in the lab, they found that more than half of them changed their orientation, indicating their sensitivity to the fields’ polarization intensity.

The researchers write that these experiments “unambiguously prove” that MagR occupies a unique biological function across many species of insects and animals. But they have more questions about how exactly the complexes work, and how they change organisms’ behavior. They don’t got into much detail about the possible applications, but from what they do say, the implications seem broad-reaching; the ability to manipulate the orientation and behavior of certain molecules or even genes could enable doctors to find novel ways to treat disease.