Guanosine-5'-triphosphate is a purine nucleoside triphosphate. It can act as a substrate for
the synthesis of RNA during the transcription process or DNA during DNA replication. Its
structure is similar to that of the guanine nucleobase, the only difference being that
nucleotides like GTP have a ribose sugar and three phosphates, with the nucleobase attached
to the 1' and the triphosphate moiety attached to the 5' carbons of the ribose.
It also has the role of a source of energy or an activator of substrates in metabolic
reactions, like that of ATP, but more specific. It is used as a source of energy for protein
synthesis and gluconeogenesis. GTP is essential to signal transduction, in
particular with G-proteins, in second-messenger mechanisms where it is converted to guanosine
diphosphate through the action of GTPases.
Uses Energy transfer
GTP is involved in energy transfer within the cell. For instance, a GTP molecule is
generated by one of the enzymes in the citric acid cycle. This is tantamount to the generation
of one molecule of ATP, since GTP is readily converted to ATP with nucleoside-diphosphate
kinase. Genetic translation
During the elongation stage of translation, GTP is used as an energy source for the binding
of a new amino-bound tRNA to the A site of the ribosome. GTP is also used as an energy
source for the translocation of the ribosome towards the 3' end of the mRNA.
Microtubule dynamic instability During microtubule polymerization, each heterodimer
formed by an alpha and a beta tubulin molecule carries two GTP molecules, and the GTP is
hydrolyzed to GDP when the tubulin dimers are added to the plus end of the growing microtubule.
Such GTP hydrolysis is not mandatory for microtubule formation, but it appears that only GDP-bound
tubulin molecules are able to depolymerize. Thus, a GTP-bound tubulin serves as a cap
at the tip of microtubule to protect from depolymerization; and, once the GTP is hydrolyzed,
the microtubule begins to depolymerize and shrink rapidly.
Mitochondrial Function The translocation of proteins into the mitochondria
matrix involves the interactions of both GTP and ATP. The importing of these proteins plays
an important role in several pathways regulated within the mitochondria organelle.
cGTP Cyclic guanosine triphosphate helps cyclic
adenosine monophosphate activate cyclic nucleotide-gated ion channels in the olfactory system.
See also GTP-gamma-S
G protein G protein-coupled receptor
5'-Guanylyl imidodiphosphate References
^ Berg, JM; JL Tymoczko; L Stryer. Biochemistry. WH Freeman
and Company. p. 476. ISBN 0-7167-4684-0. ^ Solomon, EP; LR Berg; DW Martin. Biology.
pp. 244–245. ^ Gwen V. Childs. "Microtubule structure".
cytochemistry.net. ^ Sepuri, Naresh Babu V.; Norbert Schülke
and Debkumar Pain. "GTP Hydrolysis Is Essential for Protein Import into the Mitochondrial
Matrix". Journal of Biological Chemistry: 1420–1424. doi:10.1074/jbc.273.3.1420.
^ Boron & Boulpaep. Medical Physiology. Elsevier Saunders. p. 90. ISBN 1-4160-2328-3.
External links GTP bound to proteins in the PDB