Final answer:
E3 ubiquitin ligase is key for selectivity in protein degradation, targeting proteins that are damaged, misfolded, or improperly functioning for destruction by the proteasome to maintain cellular health and stress response.
Step-by-step explanation:
The enzyme E3 ubiquitin ligase plays a crucial role in the ubiquitin-proteasomal degradation pathway. E3 ubiquitin ligase is responsible for the selectivity of protein degradation. Proteins can be targeted for degradation by E3 for various reasons, including being damaged, misfolded, or functioning improperly within the cell. The process involves marking the protein with a small protein called ubiquitin, signaling it for destruction by the proteasome. This mechanism ensures that undesirable or potentially harmful proteins are efficiently removed to maintain cellular homeostasis and respond effectively to cellular stress.
An example of the importance of E3 in the degradation pathway can be seen in its role in the regulation of the cell cycle and gene expression. Additionally, in the context of environmental stress on plants, it has been observed that certain proteins involved in degradation pathways, like the CSN subunit that regulates E3, can be induced under conditions such as aluminum stress. Similarly, the stability and function of proteins are important in hormone metabolism and signaling, as highlighted by the expression changes in radicles treated with Al, affecting pathways like ethylene and abscisic acid signaling.