Final answer:
Phosphorylation of eIF-2α makes it unavailable for protein synthesis because it cannot bind GTP, preventing the initiation complex's formation on the small (40S) ribosomal subunit, which is necessary to begin translation.
Step-by-step explanation:
The phosphorylation of eukaryotic initiation factor 2 alpha (eIF-2α) is a key regulatory step in the initiation of protein synthesis. When eIF-2α is phosphorylated, it undergoes a conformational change that prevents it from binding to guanosine triphosphate (GTP), which is necessary for the formation of the initiation complex. Therefore, the phosphorylation of eIF-2α makes it unavailable for protein synthesis, as it impedes the assembly of the necessary components on the small (40S) ribosomal subunit to begin translation.
In the context of neurodegenerative diseases like Alzheimer's, Parkinson's, and Huntington's, an increase in phosphorylation levels of eIF-2 could have detrimental effects on protein synthesis. It may lead to a decrease in the overall rate of translation or selectively block the translation of certain proteins, potentially contributing to disease pathology. This is important as changes to protein synthesis can affect the amount, function, or stability of proteins in cells.
Phosphorylation of eIF-2a makes it unavailable for protein synthesis. eIF-2a is an initiation factor that is required for the assembly of the translation initiation complex. When eIF-2a is phosphorylated, it undergoes a conformational change and cannot bind to GTP, which is necessary for the proper formation of the initiation complex and translation to occur. Therefore, phosphorylation of eIF-2a inhibits protein synthesis.