Final answer:
The eukaryotic initiation factor-2 (eIF2) is crucial for starting translation in protein synthesis. Phosphorylation of eIF2 prevents it from forming the initiation complex, thereby impeding translation. In neurodegenerative diseases, increased phosphorylation of eIF2 may block protein synthesis.
Step-by-step explanation:
The eukaryotic initiation factor-2 (eIF2) plays a critical role in the initiation of protein synthesis by forming a complex that facilitates the start of translation. Phosphorylation of eIF2 is a regulatory mechanism that can impede protein synthesis. In normal conditions, eIF2 binds guanosine triphosphate (GTP) and forms a complex with tRNA and the small 40S ribosomal subunit. This complex enables the binding of the mRNA and the subsequent recruitment of the large 60S ribosomal subunit, thus initiating translation. However, phosphorylation of eIF2 leads to its inability to bind GTP, which impedes the formation of the initiation complex and, therefore, blocks translation.
An increase in eIF2 phosphorylation observed in neurodegenerative diseases suggests a negative impact on protein synthesis, potentially blocking the translation of essential proteins. This process of regulation can be global, affecting multiple polypeptides, or specific to particular mRNA sequences that bind regulatory proteins. Translation rate and efficiency are crucially dependent on the proper functioning and regulation of eIF2 and other initiation factors.