Question

Why do we have Extrinsic Ub receptors? How do they work?

A) Enhance Ubiquitin Stability; Bind Ubiquitin Covalently
B) Facilitate Proteasome Assembly; Interact with 19S Caps
C) Increase Substrate Recognition; Non-covalent Binding to Ubiquitin
D) Inhibit Proteasomal Activity; Compete with Ubiquitin for Binding Sites

Answer 1

Extrinsic Ub receptors help to increase substrate recognition for degradation by non-covalently binding to ubiquitin. These receptors assist in the ubiquitin-proteasomal degradation pathway, crucial for several cellular processes, including protein turnover.

Step-by-step explanation:

We have Extrinsic Ub (Ubiquitin) receptors to increase substrate recognition through non-covalent binding to ubiquitin. These receptors are important because they play a crucial role in the ubiquitin-proteasomal degradation pathway, which is essential for several cellular processes such as the cell cycle, regulation of gene expression, and response to stress.

The process of ubiquitination involves several steps:

1. An ubiquitin is activated by binding to an ubiquitin-activating enzyme (E1) with the energy provided by ATP hydrolysis.
2. The activated ubiquitin is transferred to an ubiquitin-conjugating enzyme (E2).
3. Finally, the ubiquitin ligase (E3) facilitates the attachment of the ubiquitin to the target protein, marking it for degradation.

Once a protein is poly-ubiquitinated, it is delivered to the proteasome, specifically binding to one of the 19S 'CAP' structures. The ubiquitins are then released and recycled as the target protein unfolds and enters the proteasome for degradation.