GTP
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. A molecule of GTP is produced during the citric acid cycle, which can then be readily converted to ATP for a source of energy.[1]
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. In cell signalling, GTP is often hydrolysed to GDP which is then uptaken by the alpha subunit of a trimeric G protein complex.
GTP is also involved in the dynamic instability of microtubules in the cell. GTP can bind loosley to the beta-tubulin monomer of the tubilin dimer and GTP hydrolysis can occur. In the alpha-tubulin subunit it binds strongly, so GTP hydrolysis cannot occur. This causes the beta-tubulin monomer to be bound to GDP as hydrolysis can occur, and causes depolymerisation. GTP-bound alpha-tubulin polymerises due to the lack of GTP hydrolysis.[2]
GTP hydrolysis is important in nuclear transport, Ran GTPase is involved in this process. [3]
References:
- ↑ Jeremy M Berg, John L Tymoczko, Lubert Stryer. Biochemistry, 5th edition. New York: WH Freeman; 2002.page 476
- ↑ Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter. Molecular Biology of the Cell, 6th edition. Garland Science, Taylor & Francis Group, LLC. New York, 2008 page 926-927
- ↑ Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter. Molecular Biology of the Cell, 6th edition. Garland Science, Taylor & Francis Group, LLC. New York, 2008 page 653