Newly Discovered "Compass" Protein Lines Up With Magnetic Fields

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It took a long time for scientists to believe that animals were capable of sensing our planet’s magnetic field, and while we now know this so-called magnetoreception is very much a real phenomenon, researchers have yet to grasp a deep understanding of how this is achieved. Now, scientists are starting to piece together this complex puzzle, aided by the discovery of a protein complex that aligns itself with magnetic fields.

While only so far identified in flies, the genes involved are known to exist in various animals, suggesting the system is likely not confined to this one species. The work has been published in Nature Materials.

An abundance of animals – ranging from migratory birds to salmon, butterflies to lobsters – are able to detect the Earth’s magnetic field. Not just its presence, they can sense its direction and intensity too, using this information to help navigate. Simple animals can pick it up as well, like nudibranchs and termites, and use it to orient their bodies. There are even claims that humans might have such a sense, but that’s certainly up for debate.

Given its widespread presence in nature, scientists are keen to find out how it works, and some promising “magnetoreceptor” candidates have been identified in the past. Proteins called cryptochromes, for example, are the most convincing so far, with flies engineered to lack them failing to demonstrate behaviors indicative of magnetosensing. But scientists don’t think these proteins are sufficient on their own and believe there could be unidentified partners in crime.

In search for these, scientists in China, headed by Peking University’s Can Xie, scoured the genomes of the model organism Drosophila melanogaster, the fruit fly. With iron a key player in the known strongly magnetic materials of biological systems, the researchers narrowed their search by looking for iron-containing proteins that might interact with the organism’s cryptochromes.

This led them to a protein they termed MagR, a candidate magnetic receptor that they found forms complexes with a light-sensitive cryptochrome. Not only that, but it spontaneously orients itself in the direction of magnetic fields. The researchers were also able to show that these cryptochrome/MagR complexes can form in the cells of various other species, including butterflies and whales.

An interesting find, but certainly not the end to this complicated story: The researchers have yet to work out how this “compass” protein, if that is indeed what it is, actually works, so there is a lot more to be done. Still, the discovery has the potential to lead scientists towards new molecular biological techniques in the lab, such as controlling certain molecules by manipulating external magnetic fields. 

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