One Molecule of Guanosine Triphosphate is Present in Each 30S Initiation Complex

FOR some time guanosine triphosphate (GTP) has been known to be involved in the initiation of bacterial protein synthesis^1–4, although its exact function remains obscure. Although GTP stimulates the binding of fMet-tRNA to 30S ribosomes^5,6, it does not seem to be hydrolysed in the process⁷. Hydrolysis is thought to occur later, either during or immediately after the junction of the 30S initiation complex (composed of a 30S ribosome, fMet-tRNA, mRNA, initiation factor F₁ and probably other components as we shall show; and hereafter referred to as 30S i-complex) with a 50S ribosome to form a 70S initiation complex^7–9. The use to which the energy released in this hydrolysis step is put is not yet known for certain.