Image de synthèse de pompes ionique.

We finally understand the mechanism of photosensitive ion pumps!

Biochemists from theJapan Physical and Chemical Research Institute (RIKEN)discovered the mechanism of ion pumps that carry negative ions inside living cells. These ion pumps are actually proteins photosensitive. Once exposed to light, these change shape and allow anions to pass.

These works pave the way for brain research and could perhaps find many medical applications. Scientists can then transform other proteins to make them sensitive in the light in order to control them. Japanese researchers have noticed that many unicellular bacteria and algae transport ions across their cell membrane.

This ion movement allows these living beings to regulate their content and adapt to their environment. They also noted that these membrane ion pumps are light sensitive. Although many researchers have tried to understand how it works ion transporters, very few of them were really interested in negative chloride ion carriers.

A chlorine pump from a marine bacterium studied by X-ray

Researchers at the RIKEN Center used a powerful x-ray laser in order to view the shape shift of a chloride ion pump exposed to light. Mikako Shirouzu, Eriko Nango, Toshiaki Hosaka and their colleagues studied a chlorine pump coming from a marine bacteria.

Computer-generated image of ion pumps.

This ion pump is carried by the rhodopsin, a light-sensitive protein. It’s a natural pigment also present in the human eye retina. During this study, the team decided to run bromide and iodide ions through the pump. These ions are much bulkier than chloride ions and therefore more easily detectable by X-rays.

A very interesting mechanism to advance research

These ion transporters photosensitive are of great interest to biochemists and the neuroscientists. They want to use it to probe the brain circuitry of living animals by activating or deactivating certain neurons using light beams. However, they must first understand the mechanism involved inside these ion pumps in order to be able to reproduce the operation.

The researchers thus noticed that the pump is able to prevent chloride ions to go back to where they came from. This is a mechanism that only allows one one-way ion transport. Toshiaki Hosaka said that the interaction of an amino acid residue called Asn98 with the anion prevent his return after passing through the pump.


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