Proteasome Recognition and Ubiquitination Quiz

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Questions and Answers

What is the main function of the APC/C complex in cells?

Activates target proteins for cellular processes

Properly localizes proteins within the cell

Inactivates target proteins for cellular processes

Catalyzes the degradation of proteins triggering chromosome separation (correct)

Which enzyme is essential for the attachment of SUMO to other proteins?

E1 (correct)

HECT ligase

What is the main difference between ubiquitination and sumoylation?

Ubiquitination forms chains, while sumoylation does not.

SUMO activates target proteins for cellular processes.

Ubiquitin requires E1, E2, and E3 enzymes, while SUMO does not.

Ubiquitin always tags proteins for degradation, while SUMO does not. (correct)

Which type of polyubiquitin chain can activate or inactivate a target protein?

Different types of lysines producing the ubiquitin chain Signup and view all the answers

What is the role of E3 ligase in the ubiquitination process?

Attaches ubiquitin molecules to target proteins Signup and view all the answers

Which type of ligases form part of a complex with multiple subunits and possess the RING domain?

RING ligases Signup and view all the answers

What is the first step in the ubiquitination process?

Ubiquitin Activating Enzyme (E1) binds and activates an ubiquitin molecule Signup and view all the answers

What is the critical role of lysines in the ubiquitin protein?

They mediate linkage to other ubiquitin molecules in polyubiquitin chains Signup and view all the answers

What is the function of the Ubiquitin Conjugating Enzyme (E2) in the ubiquitination process?

Catalyze the transfer of ubiquitin from E2 to the target protein Signup and view all the answers

What distinguishes RING type E3 enzymes from HECT type E3 enzymes?

RING type directly catalyzes ubiquitin transfer from E2 into the target protein; HECT type does not Signup and view all the answers

How does E3 enzyme contribute to specificity in the ubiquitination system?

By recognizing both target proteins and E2 enzymes Signup and view all the answers

What is a characteristic feature of HECT ligases?

They have a catalytic site with a critical cysteine that binds ubiquitin from E2 and attaches it to a lysine in the target protein Signup and view all the answers

What is the post-translational modification process that tags proteins for degradation?

Polyubiquitination Signup and view all the answers

Which organelle is filled with plenty of hydrolytic enzymes and has an acidic pH of 4.5?

Lysosomes Signup and view all the answers

What is the large complex responsible for degrading proteins, consisting of more than 50 subunits?

Proteasome Signup and view all the answers

Which enzyme type is responsible for transferring ubiquitin to a target protein during the ubiquitination process?

Ubiquitin Conjugating Enzyme (E2) Signup and view all the answers

Which enzyme is involved in activating ubiquitin before it is transferred to the target protein during ubiquitination?

Ubiquitin Activating Enzyme (E1) Signup and view all the answers

Which type of E3 enzyme directly interacts with both the target protein and the E2 enzyme during ubiquitination?

RING ligases Signup and view all the answers

Study Notes

Ubiquitination and Sumoylation

The main function of the APC/C complex is to regulate the cell cycle by degrading specific proteins.
SUMO (Small Ubiquitin-like MOdifier) is attached to other proteins by the enzyme E1 (Activating Enzyme).
The main difference between ubiquitination and sumoylation is that ubiquitination typically targets proteins for degradation, whereas sumoylation can have various effects on protein function, such as localization, interaction, and activity.

Ubiquitination Process

The type of polyubiquitin chain that can activate or inactivate a target protein is K63-linked polyubiquitin chain.
E3 ligase plays a crucial role in the ubiquitination process by recognizing specific target proteins and facilitating the transfer of ubiquitin.
RING-type E3 ligases form part of a complex with multiple subunits and possess the RING domain.
The first step in the ubiquitination process is the activation of ubiquitin by the enzyme E1 (Activating Enzyme).
Lysines in the ubiquitin protein are critical for the formation of polyubiquitin chains.
The Ubiquitin Conjugating Enzyme (E2) plays a key role in the ubiquitination process by transferring activated ubiquitin to the target protein.
RING-type E3 enzymes differ from HECT-type E3 enzymes in that they do not form a covalent intermediate with ubiquitin.
E3 enzymes contribute to specificity in the ubiquitination system by recognizing specific target proteins and facilitating the transfer of ubiquitin.
A characteristic feature of HECT ligases is that they form a covalent intermediate with ubiquitin.

Protein Degradation

The post-translational modification process that tags proteins for degradation is ubiquitination.
The lysosome is the organelle filled with plenty of hydrolytic enzymes and has an acidic pH of 4.5.
The proteasome is the large complex responsible for degrading proteins, consisting of more than 50 subunits.
The Ubiquitin-Protein Ligase (E3) is responsible for transferring ubiquitin to a target protein during the ubiquitination process.
The Ubiquitin-Activating Enzyme (E1) is involved in activating ubiquitin before it is transferred to the target protein during ubiquitination.
RING-type E3 enzymes directly interact with both the target protein and the E2 enzyme during ubiquitination.

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Description

Test your knowledge on the recognition of proteins by the proteasome and the process of ubiquitination. Learn about the role of polyubiquitin chains and the specific lysines involved in these processes.