Glycine riboswitch
Encyclopedia
The bacterial glycine riboswitch is an RNA element
that can bind the amino acid glycine
. Glycine riboswitch
es usually consist of two metabolite-binding aptamers domains with similar structures in tandem. The aptamers cooperatively bind glycine to regulate the expression of downstream genes. In Bacillus subtilis
, this riboswitch is found upstream of the gcvT operon which controls glycine
degradation. It is thought that when glycine is in excess it will bind to both aptamers to activate these genes and facilitate glycine degradation.
Examples of the glycine riboswitch exhibit sigmoidal binding curves with Hill coefficients greater than one, indicating positive cooperativity
between the two aptamer domains. This type of binding is unusual for a riboswitch and is thought to have important physiological consequences. Glycine levels in a bacterial cell must be maintained at a certain baseline level to support protein synthesis. Positive cooperativity would allow genes for glycine degradation to be turned on more efficiently at glycine levels above this baseline concentration, which could confer a growth advantage under certain nutrient conditions.
Cis-regulatory element
A cis-regulatory element or cis-element is a region of DNA or RNA that regulates the expression of genes located on that same molecule of DNA . This term is constructed from the Latin word cis, which means "on the same side as". These cis-regulatory elements are often binding sites for one or...
that can bind the amino acid glycine
Glycine
Glycine is an organic compound with the formula NH2CH2COOH. Having a hydrogen substituent as its 'side chain', glycine is the smallest of the 20 amino acids commonly found in proteins. Its codons are GGU, GGC, GGA, GGG cf. the genetic code.Glycine is a colourless, sweet-tasting crystalline solid...
. Glycine riboswitch
Riboswitch
In molecular biology, a riboswitch is a part of an mRNA molecule that can directly bind a small target molecule, and whose binding of the target affects the gene's activity. Thus, an mRNA that contains a riboswitch is directly involved in regulating its own activity, in response to the...
es usually consist of two metabolite-binding aptamers domains with similar structures in tandem. The aptamers cooperatively bind glycine to regulate the expression of downstream genes. In Bacillus subtilis
Bacillus subtilis
Bacillus subtilis, known also as the hay bacillus or grass bacillus, is a Gram-positive, catalase-positive bacterium commonly found in soil. A member of the genus Bacillus, B. subtilis is rod-shaped, and has the ability to form a tough, protective endospore, allowing the organism to tolerate...
, this riboswitch is found upstream of the gcvT operon which controls glycine
Glycine
Glycine is an organic compound with the formula NH2CH2COOH. Having a hydrogen substituent as its 'side chain', glycine is the smallest of the 20 amino acids commonly found in proteins. Its codons are GGU, GGC, GGA, GGG cf. the genetic code.Glycine is a colourless, sweet-tasting crystalline solid...
degradation. It is thought that when glycine is in excess it will bind to both aptamers to activate these genes and facilitate glycine degradation.
Examples of the glycine riboswitch exhibit sigmoidal binding curves with Hill coefficients greater than one, indicating positive cooperativity
Cooperativity
Cooperativity is a phenomenon displayed by enzymes or receptors that have multiple binding sites where the affinity of the binding sites for a ligand is increased, positive cooperativity, or decreased, negative cooperativity, upon the binding of a ligand to a binding site...
between the two aptamer domains. This type of binding is unusual for a riboswitch and is thought to have important physiological consequences. Glycine levels in a bacterial cell must be maintained at a certain baseline level to support protein synthesis. Positive cooperativity would allow genes for glycine degradation to be turned on more efficiently at glycine levels above this baseline concentration, which could confer a growth advantage under certain nutrient conditions.