Question

Describe the composition of the 19S caps of the proteosome (2)? and each segment's function?

A) Base and Lid; Base Recognizes Ubiquitin, Lid Unfolds Substrates
B) Lid and Ring; Lid Assists in Ubiquitin Binding, Ring Initiates Hydrolysis
C) Cap and Stem; Cap Facilitates Substrate Recognition, Stem Stabilizes Substrates
D) Collar and Flap; Collar Guides Substrate Entry, Flap Secures Substrate Binding

Answer 1

The 19S caps of the proteasome consist of a Base and a Lid, where the Base recognizes ubiquitin-tagged proteins and the Lid is responsible for unfolding substrates for degradation.

Step-by-step explanation:

The 19S regulatory particle of the proteasome is involved in recognizing, binding, and preparing ubiquitinated proteins for degradation. The correct description of the composition of the 19S caps is option A) Base and Lid; where the Base recognizes ubiquitin, and the Lid unfolds substrates. After a poly-ubiquitinated protein binds to one of the 19S proteasome cap complexes, the ubiquitins are released and the substrate protein is unfolded through ATP hydrolysis. The unfolded protein then enters the 20S proteasome complex where it is digested to short peptides, which are further broken down into amino acids.