Plays a role in translation initiation. Translational GTPase that catalyzes the joining of the 40S and 60S subunits to form the 80S initiation complex with the initiator methionine-tRNA in the P-site base paired to the start codon. GTP binding and hydrolysis induces conformational changes in the enzyme that renders it active for productive interactions with the ribosome. The release of the enzyme after formation of the initiation complex is a prerequisite to form elongation-competent ribosomes. GTP + H2O = GDP + H(+) + phosphate Binds 1 monovalent cation per monomer in the active site. Structural cofactor that stabilizes the GTP-bound 'on' state. May also act as a transition state stabilizer of the hydrolysis reaction. Belongs to the TRAFAC class translation factor GTPase superfamily. Classic translation factor GTPase family. IF-2 subfamily.