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Peking University study uncovers ‘molecular compass’

ByJulia Turan

Nov 25, 2015

Feeling lost without Google Maps? Maybe you should take a hint from monarch butterflies, pigeons, whales or other creatures that can sense the Earth’s magnetic field.

Researchers in China may have determined the molecules behind up this magnetic sense, forming a ‘compass’.

50 years ago, scientists still scoffed at the idea of this sixth sense. Today, that is no longer the case. New findings from Professor Can Xie and his team at Peking University suggest a molecular duo: two proteins clumped together in a rod shape that detects magnetic field and potentially passes these signal onto the brain.

Until now, two competing theories had gone head to head: one endorsing a molecule that binds iron and the other, a light-sensing compound. Surprisingly this research lumps together these two theories.

The study authors suspected that a combination of the iron-binding and light-sensing molecules would together form a molecular compass. The light-sensing component called Cry was already found in previous research. Fruit flies without Cry have been shown to lack a magnetic sense.

Professor Xie and his colleagues scanned the fruit fly genome for a protein that would fit the bill of the iron-binding part, including ability to attach to Cry. A protein they named MagR stole the show. Together, Cry and MagR form a molecular Twinkie. MagR is the filling, and Cry is the dough.

This same pair comes together in organisms from insects to mammals, so this is not a fruit fly specific formation. The researchers specifically found the duo also forming in the retinas of pigeons. It is not yet clear whether this mini compass plays a role in our sense of direction.

The microscopic Twinkie lived up to its reputation, responding like a magnet in the lab. In fact, Cry-MagR was so magnetic that it flew up and stuck to the researchers’ iron tools.

This research is groundbreaking because it is a plausible model for the mechanism of the magnetic sense. It could even be the universal explanation for this phenomenon, cutting across species.

Although this molecular compass seems promising, it still needs to be validated in living organisms. A future experiment will need to establish if removing Cry-MagR makes for a disoriented fruit fly, ridding it of its magnetic sense.

How the mini compass passes information onto the brain is also to be determined. One idea is that as the rod rotates, this activates an attached molecule, which relays information to the brain.

The ‘Twinkie formation’ could be used to develop super sensitive magnetic sensors, with applications in mobile phone devices or mining survey systems. Even if it turns out that Cry-MagR is not the key to internal compasses, we might have a thing or two to learn from Mother Nature.

Image: Kendall Lane

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