What does eIF2 form a complex with to recruit tRNA during translation initiation?

eIF2 is a crucial initiation factor in the translation process, primarily responsible for bringing the initiator tRNA to the ribosomal small subunit. It forms a complex with GTP and the ribosomal small subunit, which acts as a platform to recruit the initiator tRNA.

The binding of GTP to eIF2 is essential for the formation of this complex because it ensures that the tRNA is brought in with high fidelity and in the correct context; GTP hydrolysis occurs after the initiator tRNA is properly positioned within the ribosomal machinery, leading to a conformational change that facilitates the assembly of the full ribosomal complex.

In contrast, the other options involve components that do not play direct roles in the recruitment of tRNA during the initiation stage of protein synthesis. GDP is involved primarily in the recycling of eIF2 after translation initiation is complete, and aminoacyl-tRNA does not directly engage with eIF2 in this context. Thus, the formation of a complex between eIF2, GTP, and the ribosomal small subunit is fundamental for the correct recruitment of tRNA during translation initiation.