Function of alpha subunits in proteasomes

[Ivaylo]

Hello! I got a question. I can not understand what is the exact function of the alpha subunits in the proteasome. It is written that it maintains the structure of the proteasome and is regulated by "regulatory particles" what are these regulatory particles and isn;t the 19S subunit that is responsible for the recognition of the polyubiquitin and so on?Thank you.

[Bluenoise]

This is a very specific question. You should link to the document that you're getting this information from if you want a resonable response.

 

Otherwise I'll just direct you to wikipedia.

 

http://en.wikipedia.org/wiki/Proteasome

 

"The outer two rings each contain seven α subunits whose function is to maintain a "gate" through which proteins enter the barrel. These α subunits are controlled by binding to "cap" structures or regulatory particles that recognize polyubiquitin tags attached to protein substrates and initiate the degradation process. The overall system of ubiquitination and proteasomal degradation is known as the ubiquitin-proteasome system."

 

Oh btw I believe that the 19S subunit is composed of 7 alpha subunites. But I maybe wrong...

*EDIT* I'm pretty sure that the above sentence is wrong. WHich is why I've gone and contradicted myself later on.

[Ivaylo]

Bluenoise, i took the info. from wikipedia, just the link u gave but it is not clear... What are there regualtory particles?

[Bluenoise]

Bluenoise, i took the info. from wikipedia, just the link u gave but it is not clear... What are there regualtory particles?

 

Try searching for polyubiquitin regulatory particle.

 

As I see it the core of the proteasome is composed of two Alpha and two beta rings. the 19s subunit is the regulatory partcle and forms a cap that feeds the peptide to be degraded into the proteolytic core.

[Ivaylo]

Well thanks anyway Bluenoise.

[Ivaylo]

Yes, that is what I thought. I supposed that these alpha subunits bond to the 19S subunit or it must be something like that, but the main role is played by the 19S.