Guanosine triphosphate
Encyclopedia
Guanosine-5'-triphosphate (GTP) is a purine
nucleoside triphosphate
. It can act as a substrate for the synthesis of RNA
during the transcription
process. Its structure is similar to that of the guanine
nucleobase
, the only difference being that nucleotides like GTP have a ribose
sugar and three phosphate
s, 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
.
GTP is essential to signal transduction
, particularly with G-proteins, in second-messenger mechanisms where it is converted to GDP
(guanosine diphosphate) through the action of GTPase
s.
. This is tantamount to the generation of one molecule of ATP
, since GTP is readily converted to ATP.
, 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.
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.
Cyclic guanosine triphosphate (cGTP) helps cyclic adenosine monophosphate
(cAMP) activate cyclic nucleotide-gated ion channel
s in the olfactory system
.
Purine
A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely distributed kind of nitrogen-containing heterocycle in nature....
nucleoside triphosphate
Nucleoside triphosphate
Nucleoside triphosphate is a nucleoside with three phosphates. Natural nucleoside triphosphates include adenosine triphosphate , guanosine triphosphate , cytidine triphosphate , 5-methyluridine triphosphate , and uridine triphosphate . These terms refer to those nucleoside triphosphates that...
. It can act as a substrate for the synthesis of RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
during the transcription
Transcription (genetics)
Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...
process. Its structure is similar to that of the guanine
Guanine
Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine . In DNA, guanine is paired with cytosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with...
nucleobase
Nucleobase
Nucleobases are a group of nitrogen-based molecules that are required to form nucleotides, the basic building blocks of DNA and RNA. Nucleobases provide the molecular structure necessary for the hydrogen bonding of complementary DNA and RNA strands, and are key components in the formation of stable...
, the only difference being that nucleotides like GTP have a ribose
Ribose
Ribose is an organic compound with the formula C5H10O5; specifically, a monosaccharide with linear form H––4–H, which has all the hydroxyl groups on the same side in the Fischer projection....
sugar and three phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
s, 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
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
, but more specific. It is used as a source of energy for protein synthesis
Protein biosynthesis
Protein biosynthesis is the process in which cells build or manufacture proteins. The term is sometimes used to refer only to protein translation but more often it refers to a multi-step process, beginning with amino acid synthesis and transcription of nuclear DNA into messenger RNA, which is then...
.
GTP is essential to signal transduction
Signal transduction
Signal transduction occurs when an extracellular signaling molecule activates a cell surface receptor. In turn, this receptor alters intracellular molecules creating a response...
, particularly with G-proteins, in second-messenger mechanisms where it is converted to GDP
Guanosine diphosphate
Guanosine diphosphate, abbreviated GDP, is a nucleoside diphosphate. It is an ester of pyrophosphoric acid with the nucleoside guanosine. GDP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase guanine....
(guanosine diphosphate) through the action of GTPase
GTPase
GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate . The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases.-Functions:...
s.
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 cycleCitric acid cycle
The citric acid cycle — also known as the tricarboxylic acid cycle , the Krebs cycle, or the Szent-Györgyi-Krebs cycle — is a series of chemical reactions which is used by all aerobic living organisms to generate energy through the oxidization of acetate derived from carbohydrates, fats and...
. This is tantamount to the generation of one molecule of ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
, since GTP is readily converted to ATP.
Genetic Translation
During the elongation stage of translationTranslation (genetics)
In molecular biology and genetics, translation is the third stage of protein biosynthesis . In translation, messenger RNA produced by transcription is decoded by the ribosome to produce a specific amino acid chain, or polypeptide, that will later fold into an active protein...
, GTP is used as an energy source for the binding of a new amino-bound tRNA to the A site of the ribosome
Ribosome
A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....
. 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 microtubuleMicrotubule
Microtubules are a component of the cytoskeleton. These rope-like polymers of tubulin can grow as long as 25 micrometers and are highly dynamic. The outer diameter of microtubule is about 25 nm. Microtubules are important for maintaining cell structure, providing platforms for intracellular...
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.
cGTP
Cyclic guanosine triphosphate (cGTP) helps cyclic adenosine monophosphate
Cyclic adenosine monophosphate
Cyclic adenosine monophosphate is a second messenger important in many biological processes...
(cAMP) activate cyclic nucleotide-gated ion channel
Cyclic nucleotide-gated ion channel
Cyclic nucleotide-gated ion channels are ion channels that function in response to the binding of cyclic nucleotides. CNG channels are nonselective cation channels that are found in the membranes of various types of cells.- Discovery :...
s in the olfactory system
Olfactory system
The olfactory system is the sensory system used for olfaction, or the sense of smell. Most mammals and reptiles have two distinct parts to their olfactory system: a main olfactory system and an accessory olfactory system. The main olfactory system detects volatile, airborne substances, while the...
.
See also
- GTP-gamma-SGTPgammaSGTPgammaS is nonhydrolyzable G-protein-activating analog of guanosine triphosphate...
- G proteinG proteinG proteins are a family of proteins involved in transmitting chemical signals outside the cell, and causing changes inside the cell. They communicate signals from many hormones, neurotransmitters, and other signaling factors. G protein-coupled receptors are transmembrane receptors...
- G protein coupled receptor
- 5'-Guanylyl imidodiphosphate5'-Guanylyl imidodiphosphate5'-Guanylyl imidodiphosphate is a purine nucleotide. It is an analog of guanosine triphosphate in which one of the oxygen atoms is replaced with an amine, producing a non-hydrolyzable functional group. Guanylyl imidodiphosphate binds tightly to G-proteins in the presence of Mg2+. Guanylyl...