Final answer:
Misfolded proteins are tagged for degradation by the E3 ligase which recognizes specific degradation signals and facilitates ubiquitin attachment, resulting in proteasomal degradation.
Step-by-step explanation:
The process of recognizing and tagging misfolded proteins by the E2-E3 ligase complex is a critical function in cellular biology, particularly within the ubiquitin-proteasomal pathway. This pathway is integral to a variety of cellular processes, including protein degradation and modification, as well as the response to stressors like oxidative stress. To ensure protein quality control, the cell utilizes ubiquitin, a 76-amino acid polypeptide, which marks proteins for degradation by attaching to them and delivering them to the proteasome, a large complex of polypeptides.
Within the ubiquitin-proteasomal degradation pathway, proteins are managed by different enzymes such as ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), and ubiquitin ligases (E3), with E3 being crucial for the specificity of protein degradation. When proteins are misfolded or malfunctioning, the E3 ligase recognizes specific degradation signals on these proteins and facilitates the attachment of ubiquitin chain. This poly-ubiquitination serves as a signal to the proteasome to degrade the tagged protein. In the proteasome, ATP hydrolysis unfolds the target protein which is then fed into the core where proteolytic enzymes break it down into peptide fragments.