Editing Proteasome (section)

===Other regulatory particles===
{{Redirect-distinguish|11S|S11 (disambiguation){{!}}S11|11 (disambiguation){{!}}11 (plural)}}

==== 11S ====
20S proteasomes can also associate with a second type of regulatory particle, the 11S regulatory particle, a heptameric structure that does not contain any ATPases and can promote the degradation of short [[peptide]]s but not of complete proteins. It is presumed that this is because the complex cannot unfold larger substrates. This structure is also known as PA28, REG, or PA26.<ref name="pmid21211719">{{cite journal |last1=Stadtmueller |first1=BM |last2=Hill |first2=CP |title=Proteasome activators. |journal=Molecular Cell |date=7 January 2011 |volume=41 |issue=1 |pages=8–19 |doi=10.1016/j.molcel.2010.12.020 |pmid=21211719 |pmc=3040445}}</ref> The mechanisms by which it binds to the core particle through the C-terminal tails of its subunits and induces α-ring [[conformational change]]s to open the 20S gate suggest a similar mechanism for the 19S particle.<ref name=Forster>{{cite journal | vauthors = Förster A, Masters EI, Whitby FG, Robinson H, Hill CP | title = The 1.9 A structure of a proteasome-11S activator complex and implications for proteasome-PAN/PA700 interactions | journal = Molecular Cell | volume = 18 | issue = 5 | pages = 589–99 | date = May 2005 | pmid = 15916965 | doi = 10.1016/j.molcel.2005.04.016 | doi-access = free }}</ref> The expression of the 11S particle is induced by interferon gamma and is responsible, in conjunction with the immunoproteasome β subunits, for the generation of peptides that bind to the [[major histocompatibility complex]].<ref name=Wang/>

==== BLM10/PA200 ====
Yet another type of non-ATPase regulatory particle is the Blm10 (yeast) or PA200/[[PSME4]] (human). It opens only one α subunit in the 20S gate and itself folds into a dome with a very small pore over it.<ref name="pmid21211719"/>

==== Archaeal Proteasomes ====
[[Archaea]] also contain a proteasome degradation pathway with a 20S core and a regulatory particle consisting of the Proteasome-Activating Nucleotidase (PAN), that shares similarities to the 19S proteasome.  Like the eukaryotic 19S, PAN is a [[AAA-ATPase]], containing N-terminal coiled coils, an OB ring, an ATPase domain with an HBXY motif that interacts with the archaeal 20S.

==== Bacterial Proteasomes ====
Actinobacteria have acquired a proteasome degradation pathway, including its own 20S core particle and a [[AAA proteins|AAA protein]] motor, MPA (mycobacterial proteasome activator).  Unlike the base subcomplex of the 19S, MPA is a homohexameric motor complex, containing the ATPase sites, a tandem (oligosaccharide/oligonucleotide-binding) OB ring, and [[Coiled coil]]s that extend off N-termini off the OB ring.  The C-terminus contains HBXY motifs that contact the 20S core particle in a similar way as with other regulatory particles.  Targeting to MPA requires a prokaryotic protein, [[Prokaryotic ubiquitin-like protein]] (or Pup) that functions as ubiquitin as a tag that can be attached to a protein substrate, though the structure of Pup is unrelated to that of ubiquitin.  Once attached, a puplyated protein can be targeted to MPA through the coiled-coil and can be directed through the AAA motor into the 20S for degradation.<ref>{{cite journal |last1=Kavalchuk |first1=Mikhail |last2=Jomaa |first2=Ahmad |last3=Müller |first3=Andreas U. |last4=Weber-Ban |first4=Eilika |title=Structural basis of prokaryotic ubiquitin-like protein engagement and translocation by the mycobacterial Mpa-proteasome complex |journal=Nature Communications |date=12 January 2022 |volume=13 |issue=1 |page=276 |doi=10.1038/s41467-021-27787-3|pmid=35022401 |pmc=8755798 |bibcode=2022NatCo..13..276K }}</ref><ref>{{cite journal |last1=Striebel |first1=F |last2=Hunkeler |first2=M |last3=Summer |first3=H |last4=Weber-Ban |first4=E |title=The mycobacterial Mpa-proteasome unfolds and degrades pupylated substrates by engaging Pup's N-terminus. |journal=The EMBO Journal |date=7 April 2010 |volume=29 |issue=7 |pages=1262–71 |doi=10.1038/emboj.2010.23 |pmid=20203624|pmc=2857465 }}</ref>