Turning Off A Protein By Turning On A Light | Chemical & Engineering News
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Web Date: November 14, 2013

Turning Off A Protein By Turning On A Light

Molecular Biology: Researchers triggered the degradation of a protein by attaching it to a light-sensitive domain that can recruit the cell’s protein disposal system
Department: Science & Technology | Collection: Life Sciences
News Channels: Biological SCENE, Analytical SCENE
Keywords: light-responsive protein, proteasome, degron
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Light ’Em Up
Researchers tagged a protein of interest (POI) with a light-sensitive domain (B-LID) that includes a degradation signal called a degron (green). In the dark, the degron is hidden within the light-sensitive domain. Blue light triggers a conformational change that exposes the degron (red), signaling an enzyme complex to come and degrade the protein of interest (far right).
Credit: ACS Chem. Biol.
Scheme for new blue-light-powered switch that lowers the level of proteins inside a cell.
 
Light ’Em Up
Researchers tagged a protein of interest (POI) with a light-sensitive domain (B-LID) that includes a degradation signal called a degron (green). In the dark, the degron is hidden within the light-sensitive domain. Blue light triggers a conformational change that exposes the degron (red), signaling an enzyme complex to come and degrade the protein of interest (far right).
Credit: ACS Chem. Biol.

If biochemists could dial in more or less of a certain protein in a cell, they could then watch how the cell responds to determine that protein’s role. Now researchers report a simple dimmer switch that lowers levels of a protein inside a cell using blue light (ACS Chem. Biol. 2013, DOI: 10.1021/cb400755b).

Most systems that use light to alter protein levels require two or more genetic tweaks to cells, says Kimberly M. Bonger, now at Radboud University, in Nijmegen, the Netherlands. She and her colleagues wanted to develop a method that worked with just one—the insertion of a light-sensitive domain into their gene of choice—to make the method easier to apply to a wide range of proteins.

The key to this simplification was a four-amino-acid sequence called a degron, which tells the proteasome—an enzyme complex that acts as the cell’s garbage disposal—to chew up the protein labeled with that sequence. To degrade a protein of interest, Bonger, while in the laboratory of Thomas J. Wandless at Stanford University, linked a degron to a light-sensitive protein domain called LOV2. In the dark, LOV2 folds up, and that hides the degron. But, when excited with blue light, the domain unfolds, exposing the degron and unleashing the wrath of the proteasome. Blue light doesn’t harm cells, so the switch shouldn’t affect any cellular function on its own.

To test the method, the researchers expressed the gene for yellow fluorescent protein with the LOV2-degron tag in mouse fibroblast cells. In the dark, the fluorescent signal from the cells was strong. After exposing the cells to blue light for two hours, the fluorescence decreased by 80 to 90%, signaling the protein’s demise.

Bonger plans to use the method to turn genes off and on by attaching the light-sensitive protein domain to transcription factors.

 
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Comments
Cornell Student in Bioengineering (February 23, 2014 8:26 PM)
As a student as well as a proponent of imaginative-based learning and simplicity in scientific explanations, I have to say that this is one of the clearest explanations I've seen in a research journal. "...acts as the cell's garbage disposal...", "...unleashing the wrath of the proteasome." THAT'S the kind of writing that engages me to the science. So thank you for that.

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