GTP

Displayed formula of guanosine triphosphate showing the three regions of the molecule: the guanine base, ribose sugar and the triphosphate arm.

Guanosine triphosphate (GTP) is one of the nucleotides that make up an RNA molecule. It consists of a ribose sugar, which is attached to a guanine heterocyclic base on C1' of the sugar and a triphosphate group on C4' of the sugar.
It is similar to ATP which is widely utilised in many cellular processes as a source of energy. Dephosphorylation of GTP also yields energy, but the use of GTP in this manner is more specific to certain metabolic pathways.

GTP is used in protein synthesis. During initiation of translation, the GTP is associated with an initiation factor 2 (IF₂) and is hydrolysed upon the assembly of the initiation ribosomal complex. During elongation, GTP facilitates the binding of a new aminoacyl tRNA to the A site at a ribosome.

GTP is also an important factor in signal transduction pathways. Here, GTP can be associated with G-protein complexes and is used to regulate the activity of the protein.