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Home >> Dictionary of Bioinformatics, Biochemistry, Biotechnology >> Group II Hormones - GTPase Activating Protein (GAP)
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Griseofulvin
An antifungal agent produced by Penicillium griseofulvum that inhibits the movement of chromosome during mitosis by interfering with the spindle apparatus.
Ground state
The lowest electronic energy state of an atom or a molecule.
Group III introns (Spliceosomal introns)
Introns found in nuclear mRNA primary transcripts. The splicing mechanism is similar to that of group II introns and involves formation of a lariat structure.
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Group I hormone
Hormones that bind to intracellular receptors such as steroid hormones, calcitriol, retinoic acid and the thyroid hormones. These are lipophilic and are transported in circulation bound to transport proteins, which prolong their plasma half lives. The hormone-receptor complex is responsible for signal transduction.
Group II hormones
Hormones that bind to cell surface receptors and mediates their effects through intermediary molecules termed second messengers. Hormones in this group include catecholamines, polypeptides, proteins and glycoprotein hormones. These are water-soluble and bind to receptors located in the plasma membrane of the target cell. The hormone-receptor interaction influences intracellular metabolic process via second messengers such as cyclic 3’,5-adenosine monophosphate (c-AMP), cyclic guanosine monophosphate (c-GMP), etc.
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Group I introns
A class of introns found in mitochondrial genomes, nuclear genomes of unicellular eukaryotes (eg. rRNA genes of Tetrahymena thermophila) and in the rare introns of prokaryotic systems. These are autocatalytic and do not require ATP.
Group II introns
Introns found in the primary transcripts of mitochondrial or chloroplast mRNAs in fungi, algae and plants. The mechanism of splicing closely resembles that used by nuclear premRNA introns.
Group IV introns
Introns found in certain tRNAs. The splicing reaction requires ATP and an endonuclease.
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Group transfer potential
An index of the ability of a compound to donate an activated group (phosphate or acyl). It is usually expresses as the standard frr energy of hydrolysis.
Group translocation
A type of active transport in which compounds transported into the cell by passive diffusion undergo modification by phosphorylation. As a result, these compounds cannot diffuse back across the cell membrane and are trapped in the cytoplasm.
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Growth cabinet
A cupboard used for the incubation of tubes or culture vessels under controlled environmental conditions.
Growth cone
The migrating motile tip of an axon or a dendrite.
Growth curve
A graph in which the number of individuals in a population of organisms such as cells in culture is plotted as function of time.
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Growth curve
A substance that must be present in the growth medium to permit cell proliferation. Most growth factors are polypeptides by binding to the cell surface receptors.
Growth fork
The region on a DNA molecule where synthesis is taking place. The region of duplex DNA connected to a region of unwound single strands gives the shape of a fork. Also known as replication fork.
Growth hormone (GH) (somatotrophin; somatotrophin)
A hormone, secreted by the maintain anterior pituitary gland, that influences a number of physiological and biochemical process. GH stimulates of long bones, protein synthesis, and breakdown of fats. GH secretion is regulated by the opposing actions of two hypothalamic hormones: somatocrinin (growth-hormone-releasing hormone), which promoters GH release; and somatostatin (growth-hormone-inhibiting hormone), that inhibits the release of GH from the anterior pituitary gland.
Growth hormone (GH) receptor
A protein with a single membrane spanning domain. Binding of GH causes dimerisation of two GH receptors resulting in phosphorylation of the receptor and activation of GH receptor associated JAK2 tyrosine kinase and a number of signalling pathways.
Growth hormone-release inhibiting hormone (GHRIH, somatostatin)
See somatostatin.
Growth hormone-releasing hormone (GHRH)
A polypeptide hormone that stimulates GH release. It contains 44 amino acid residues and belongs to a family of molecules that includes secretin, glucagon, vasoactive intestinal peptide (VIP) and gastric inhibitory polypeptide (GIP). The stimulation of GH release by GHRH is calcium dependent and mediates by c-AMP. GHRH is reported to activate GH gene transcription by stimulating c-fos, a growth signal transducing oncogene.
Growth inhibitor
Any substance that inhibits the growth of an organism. The inhibition may be mild (growth retardation) or severe, and in extreme cases leading to death (toxic reaction). Two plant growth regulators that function as inhibitors are ethylene and abscisic acid. The extent of inhibition depends in several factors such as concentration of the inhibitor, length of exposure and the relative susceptibility of the organisms exposed to the inhibitor.
Growth media
A synthetic solution of nutrients that supports the growth of cells or microorganisms in culture.
Growth phases; growth phase curve
The characteristic periods in the growth of a bacterial culture, as seen in a graph of viable cell number versus time, namely: lag phase; logarithmic (or exponential) phase; stationary phase and death phase.
Growth rate
Increase in mass per unit time.
Growth regulator
See plant growth regulator.
Growth retardant
A chemical that selectively interferes with normal hormonal promotion of growth and other physiological process, but does not exhibit toxic effects.
Grunstein and Hogness method
The technique of hybridisation of a DNA probe to whole, lysed bacterial colonies that have been transferred to a nitrocellulose membrane by blotting; colony hybridisation.
Gs
See stimulatory G protein.
GSS (Genome survey sequence)
A random, single pass genomic DNA sequence.
GT-AG rule
The presence of these dinucleotides signal the beginning (GT) and end (AG) of introns of nuclear genes.
GTP
Guanosine triphosphate synthesised by phosphorylation of guanosine diphosphate (GDP). It releases a large amount of free energy on hydrolysis. It plays an important role in cell signalling microtubule assemble and protein biosynthesis.
GTPase
An enzyme that breaks down GTP to GDP. It is also a common name for monomeric GTP-binding proteins. See GTP-binding protein.
GTPase-activating protein (GAP)
A protein that binds to a GTP-binding protein and inactivates it by stimulating its GTPase activity and hydrolyzing the bound GTP to GDP.
GTPase superfamily
A group of intracellular switch proteins that alternate between an inactive GDP-bound state and an active GTP-bound state. These proteins are involved in regulating various cellular processes. The members of this family include. the Gα subunit of trimeric (large) G proteins and monomeric (small) G proteins such as Ras, Rab, Ran and Rac as well as elongation factors used in protein biosynthesis.
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