Cop this! The protein ‘cop’ (Cop9) with multiple tasks

What is it?

The human signalosome complex (also known as COP9 signalosome or CSN) acts like a police cop within our cells. Like a policeman, it has multiple jobs, from defense to development. In particular, it serves our cell by ‘policing’ the large quantity of proteins in our cells. If certain proteins get out of hand, Cop9 plays a role in their degradation or removal.

Cop9 is vital for maintaining normal cellular function. It coordinates around 20% of all protein degradation in the body. If the protein malfunctions, a whole range of problems can ensue. This may lead to problems during our development. Cop9 has also been linked to breast and liver cancer, making it an attractive drug target for novel cancer therapies.

What does it look like?

Cop9 is massive. It contains eight individual domains (coloured separately below), six of which form a ‘horseshoe’ shape. Due to its massive size, Cop9 can perform a whole lot of different functions, and these individual functions are highly regulated.

The structure of Cop9 with its eight domains coloured separately (NB- its overall dimensions are 173 x 142 x 108Å). Image generated by Pymol (http://www.pymol.org/) (pdb code: 4D10 http://www.pdb.org/pdb/explore/explore.do?structureId=4D10)

The structure of Cop9 with its eight domains coloured separately (NB- its overall dimensions are 173 x 142 x 108Å). Image generated by Pymol (http://www.pymol.org/) (pdb code: 4D10 http://www.pdb.org/pdb/explore/explore.do?structureId=4D10)

Where did the structure come from?

The structure of the human COP9 signalosome was determined by X-ray crystallography. Because it is such a large complex, this was not an easy feat. It required a team of dedicated and expert researchers. The structure was published only a few months ago (August 2014) in Nature (http://www.nature.com/nature/journal/v512/n7513/full/nature13566.html). This new structure provides vital insight into how the complicated protein Cop9 performs its duties.

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