Elongation factors Tu and G change their conformation on interaction with ribosomes

Limited trypsinolysis was used to study conformational changes in elongation factors Tu and G. The trypsin cleavage rates of the factors differed and depended on both their interaction with ligands and the presence or absence of ribosomes. When the factors were bound to ribosomes, changes in their sensitivity to trypsin were observed depending on whether GDP or GTP was present in the complex, i.e. on the hydrolysis state of the guanine nucleotide ligand. The possible significance of factor structural changes for their functioning is discussed.