Multiple Choice
Which of the following statements about ubiquitin is TRUE?
7. Enzyme Inhibition and Regulation
Ubiquitination
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Which of the following best describes the action of the enzyme ubiquitin ligase?
A
It directly degrades proteins in the proteasome.
B
It catalyzes the attachment of ubiquitin to target proteins, marking them for degradation.
C
It removes ubiquitin from proteins, reversing ubiquitination.
D
It hydrolyzes ATP to provide energy for protein folding.
Verified step by step guidance1
Understand the role of ubiquitin ligase: Ubiquitin ligase is an enzyme involved in the process of protein degradation. It does not directly degrade proteins but plays a key role in marking them for degradation.
Learn about ubiquitination: Ubiquitination is a post-translational modification where ubiquitin, a small regulatory protein, is attached to target proteins. This process signals the proteasome to degrade the marked proteins.
Identify the specific action of ubiquitin ligase: Ubiquitin ligase catalyzes the attachment of ubiquitin to lysine residues on target proteins. This step is crucial for tagging proteins for degradation.
Clarify what ubiquitin ligase does NOT do: Ubiquitin ligase does not remove ubiquitin from proteins (this is done by deubiquitinating enzymes), nor does it hydrolyze ATP for protein folding. It specifically facilitates ubiquitin attachment.
Relate ubiquitin ligase to the proteasome: Once ubiquitin is attached to a protein, the proteasome recognizes the ubiquitinated protein and degrades it. Ubiquitin ligase sets the stage for this process by tagging the protein.
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