Final answer:
The release of other initiation factors, allowing the ribosomal subunits to associate in eukaryotic cells, is caused by the hydrolysis of GTP on eIF2. This process is essential for the formation of a functional ribosome and is tightly regulated to control protein synthesis rates.
Step-by-step explanation:
In eukaryotic cells, the factor that causes the release of other initiation factors, allowing the large and small ribosomal subunits to associate, is the hydrolysis of GTP on eukaryotic initiation factor 2 (eIF2). Once the initiation complex is formed and the initiator tRNA anticodon is paired with the start AUG codon on mRNA, this event occurs. The hydrolysis process converts GTP to GDP, which remains bound to eIF2.
Consequently, this triggers the disassembly of the initiation factors, which is a prerequisite for the large (60S) ribosomal subunit to join the small (40S) subunit and create a functional ribosome ready for translation. The regulation of eIF2's capacity to acquire a new GTP molecule, which is necessary for another round of initiation, is facilitated by another initiation factor known as eIF2B.
The GTP/GDP exchange facilitated by eIF2B essentially recycles GTP-bound eIF2 for subsequent initiation events. It's also important to note that the regulation of eIF2 function can impact translation rates. When eIF2 is phosphorylated it cannot bind GTP, which impedes formation of the initiation complex and thereby slows down or halts protein synthesis.