Question

Describe the detailed composition of a 26S proteosome & its function?

A) 19S Cap, 6S Core; Degrades Misfolded Proteins
B) 20S Core, 7S Cap; Facilitates Protein Folding
C) 18S Cap, 8S Core; Initiates DNA Replication
D) 17S Cap, 9S Core; Regulates RNA Synthesis

Answer 1

The 26S proteasome is composed of a 20S proteasome core and 19S proteasome cap complexes, functioning to degrade misfolded or unneeded proteins in the cell. Proteins are tagged with ubiquitin, unfolded by the 19S cap, and broken down into peptides and amino acids by the 20S core.

Step-by-step explanation:

The detailed composition of a 26S proteasome includes a 20S proteasome core complex and one or two 19S proteasome cap complexes. This sophisticated cellular machine's function is to degrade misfolded or no longer needed proteins within the cell. Proteins targeted for degradation are typically tagged with ubiquitin, a small regulatory protein, and then delivered to the 26S proteasome. Upon binding to the 19S cap, these poly-ubiquitinated proteins are then deconstructed: the ubiquitins are recycled, the target proteins are unfolded and fed into the 20S core, where they are broken down into short peptides by proteolytic enzymes. These peptides are further degraded into free amino acids in the cytoplasm.