Tiny protein ‘compasses’ found in fruit flies – and potentially humans

Tiny biological compasses made from clumps of protein may
help scores of animals, and potentially even humans, to find their way around,
researchers say.

Scientists discovered the minuscule magnetic field sensors
in fruit flies, but found that the same protein structures appeared in retinal
cells in pigeons’ eyes. They can also form in butterfly, rat, whale and human
cells.

The rod-like compasses align themselves with Earth’s
geomagnetic field lines, leading researchers to propose that when they move,
they act on neighbouring cell structures that feed information into the nervous
system to create a broader direction-sensing system.

Professor Can Xie, who led the work at Peking University,
said the compass might serve as a “universal mechanism for animal magnetoreception,”
referring to the ability of a range of animals from butterflies and lobsters to
bats and birds, to navigate with help from Earth’s magnetic field.

Whether the compasses have any bearing on human navigation
is unknown, but the Peking team is investigating the possibility. “Human sense
of direction is complicated,” said Xie. “However, I believe that magnetic sense
plays a key role in explaining why some people have a good sense of direction.”

The idea that animals could sense Earth’s magnetic field was
once widely dismissed, but the ability is now well established, at least among
some species. The greatest mystery that remains is how the sensing is done.

One type of molecular compass, proposed by the biologist
Klaus Schulten, senses geomagnetic field information through the bizarre
quantum behaviour of electrons that are produced when light falls on retinal
proteins called cryptochromes. But Xie argues that a compass based on cryptochromes
alone is not enough to navigate.

By screening the fruit fly genome, the Chinese team
discovered a protein they named MagR, which forms rod-like clumps with
cryptochrome proteins. This MagR-cryptochrome cluster behaves like a
sophisticated magnetic sensor that in principle can sense the direction,
intensity or inclination of Earth’s magnetic field.

“The nanoscale biocompass has the tendency to align itself
along geomagnetic field lines and to obtain navigation cues from a geomagnetic
field,” said Xie. “We propose that any disturbance in this alignment may be
captured by connected cellular machinery, which would channel information to
the downstream neural system, forming the animal’s magnetic sense.”

In a series of follow-up experiments, the scientists show
that MagR-cryptochrome compass can form in a range of species, including
monarch butterflies, pigeons, more rats, minke whales and humans. Details are
reported in the journal Nature Materials.

Xie said the discovery could go beyond understanding how
animals navigate, and lead to new technologies that allow scientists to control
cell processes and influence animal behaviour with magnetic fields.

Simon Benjamin, who studies quantum materials at Oxford
University, said that evolution seemed to have found a number of ways to sense
magnetic fields. “It seems plausible that the structure discovered in this
paper is key to the fruit fly’s compass, and perhaps other species as well.”

He added that the finding was exciting even if the
MagR-cryptochrome cluster was not one of nature’s biocompasses, because it
could be used to develop new technologies. “There is a continual drive for
cheaper, smaller, more robust, or more sensitive field sensors. They’re needed
to enable a vast range of applications from mining survey systems to map
navigation with mobile phones.”

“It has been well documented that cryptochromes, which are
crucial to the compass proposed in this new paper, may harness significant
quantum effects to convert the Earth’s weak magnetic field into a signal in the
animal’s brain. 

This is a tantalising possibility since the new UK quantum
technology hubs are focusing about a quarter of their £150M on sensor systems.
It would be remarkable if we can learn some tricks from Mother Nature in this
highly-advanced field of physics,” he added.

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Posted on November 18, 2015, in Useful Information. Bookmark the permalink. Leave a comment.

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