Question

In the proteasome, the unfolded protein is threaded through narrow opening in the ring of ___________________

(a) ligase

(b) sigma factor

(c) alpha-subunit

(d) beta-subunit

The question was posed to me during an interview.

Question is taken from Gene Expression Control in portion Control of Gene Expression of Cell Biology

Answer 1

The correct answer is:

(c) alpha-subunit

Explanation:

In the proteasome, the unfolded protein is threaded through a narrow opening in the ring of alpha-subunits. The proteasome is a complex enzyme responsible for degrading unneeded, damaged, or misfolded proteins by proteolysis. It has a cylindrical structure composed of a core particle (20S) and regulatory particles. The core particle contains alpha-subunits on the outside, which form the gate that controls access to the inner catalytic sites, and beta-subunits on the inside, which perform the proteolytic cleavage. The unfolded protein is recognized and unfolded by the regulatory particles and then threaded through the alpha-subunit ring into the interior of the proteasome, where it is broken down into smaller peptides.