Page 60 - Cell biology PDC 2024
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C- Finally, E3 (ubiquitin ligase) interacts with both E2-ubiquitin and the
protein that will be destroyed by transferring the ubiquitin to the target
protein. This occurs many times resulting in a polyubiquitinated protein
that is sent to the proteasome for destruction.
Figure 27: Ubiquitination of proteins
Proteasomes are very large protein complexes in a form of as four-
layered barrel called the 20S subunit. This barrel is capped by a
regulatory subunit called 19S on each end of the barrel. The entire
proteasome is sometimes referred to as a 26S particle
The two outer caps or rings are each composed of 7 α subunits that act as
entry gates to the central rings (each of which is composed of 7 β
subunits), and which also contain 6 proteolytic sites.
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