This picture shows a cartoon of how the switch works. Left: this configuration of the L3 finger switch places the ribosome in the "open" position, where it binds the protein that delivers new tRNAs to it (eEF1A-aatRNA-GTP). The tRNAs are then delivered to the ribosomal core in a process called "accommodation". Once there, they participate in the central step of protein synthesis called peptidyltransfer. During this time, the L3 switch moves, closing the ribosome, and forming the binding site for the next player called eEF2-GTP, whose function is to push the ribosome down the mRNA, setting up the next step in the cycle of protein synthesis.