Histidine operon leader
Encyclopedia
The Histidine operon leader is an RNA element
found in the bacteria
l histidine
operon
. At least 6 amino acid operons are known to be regulated by attenuation
. In each a leader sequence of 150-200 bp is found upstream of the first gene in the operon. This leader sequence can assume two different secondary structures known as the terminator and the anti-terminator structure. In each case the leader also codes for very short peptide sequence that is rich in the end product amino acid of the operon. The terminator structure is recognised as a termination signal for RNA polymerase and the operon is not transcribed. This structure forms when the cell has an excess of the regulatory amino acid and ribosome movement over the leader transcript is not impeded. When there is a deficiency of the charged tRNA of the regulatory amino acid the ribosome translating the leader peptide stalls and the antiterminator structure can form. This allows RNA polymerase to transcribe the operon.
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...
found in the bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
l histidine
Histidine
Histidine Histidine, an essential amino acid, has a positively charged imidazole functional group. It is one of the 22 proteinogenic amino acids. Its codons are CAU and CAC. Histidine was first isolated by German physician Albrecht Kossel in 1896. Histidine is an essential amino acid in humans...
operon
Operon
In genetics, an operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single regulatory signal or promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo trans-splicing to create...
. At least 6 amino acid operons are known to be regulated by attenuation
Attenuation
In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by lead, and light and sound are attenuated by water.In electrical engineering and telecommunications, attenuation affects the...
. In each a leader sequence of 150-200 bp is found upstream of the first gene in the operon. This leader sequence can assume two different secondary structures known as the terminator and the anti-terminator structure. In each case the leader also codes for very short peptide sequence that is rich in the end product amino acid of the operon. The terminator structure is recognised as a termination signal for RNA polymerase and the operon is not transcribed. This structure forms when the cell has an excess of the regulatory amino acid and ribosome movement over the leader transcript is not impeded. When there is a deficiency of the charged tRNA of the regulatory amino acid the ribosome translating the leader peptide stalls and the antiterminator structure can form. This allows RNA polymerase to transcribe the operon.