 Upon GTP hydrolysis, the conformation of EF-Tu changes drastically and dissociates from the aa-tRNA and ribosome complex.The aa-tRNA then fully enters the A-site, where its amino acid is brought near the P-site's polypeptide and the ribosome catalyzes the covalent transfer of the polypeptide onto the amino acid.In the cytoplasm, the deactivated EF-Tu • GDP is acted on by the prokaryotic elongation factor EF-Ts, which causes EF-Tu to release its bound GDP.