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Channelrhodopsin - Some Background Info

What are channelrhodopsins? Channelrhodopsins are a class of proteins that respond quickly to, and have high sensitivity to, light intensities.

In what organism are channelrhodopsins found? How do they help this organism survive? Found mainly in blue-green algae (Chlamydomonas reinhardtii), channelrhodopsin proteins register when there is a lack of light, and generate signals that assist the organism in finding a location with better conditions for photosynthesis. Because of these molecules, algae can live in benthic regions of soil - where the conditions are not ideal for photosynthesis.

The History of the Discovery of Channelrhodopsin In 2002, Goerg Nagel and his colleagues were credited with the discovery of Channelrhodopsin-1. It was first noticed in Chlamydomonas reinhardtii because it is a light-activated channel. Channelrhodopsin-2 was later isolated from Chlamydomonas reinhardtii as well, in 2005 by the Deisseroth neurobiology group. It had been noticed, long before, that blue-green algae could sense and move towards light - despite lacking eyes - but only recently had independent group had a breakthrough: identifying examples of the gene that allowed algae to sense light without eyes. Going through the algae genome, it was noticed that retinal pigments and the new molecules were genetically similar and both were photosensitive, but they transmitted signals differently. The new molecules could sense light and act as ion channels, generating electrical signals. Upon testing the channels in a lab dish, it was discovered that some channels, like channelrhodopsin, could "activate" cells by sending out signals, while some light-activated ion channel pumps could "inhibit" cells by signaling them to shut down. Researchers were then able to conclude that light directly opened these channels, allowing ions to flow through and control neuron electrical activity.


A picture of channelrhodopsin, courtesy of http://www.sfn.org/skins/main/images/rd/light_molecules/deisseroth.jpg. This is from the Deisseroth Neurobiology Group page. Yes, as in the group credited with the discovery of Channel-rhodopsin 2 in 2005. This is a picture of the actual molecule in a cell. The red is the synapses, contact points between cells, and the green is the actual molecule - which is photosensitive (light sensitive).

Pretty awesome, right? We thought so too.