- Threonine operon leader
The threonine operon leader is an RNA element. Threonine is one of at least 6
amino acid operon s are known to be regulated byattenuation .cite journal | last = Kolter | first = R | coauthors = Yanofsky C | year = 1982 | title = Attenuation in amino acid biosynthetic operons | journal = Annu Rev Genet | volume = 16 | pages = 113–134 | pmid = 6186194 | doi = 10.1146/annurev.ge.16.120182.000553] 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 chargedtRNA of the regulatory amino acid theribosome translating the leader peptide stalls and the antiterminator structure can form. This allowsRNA polymerase to transcribe the operon.References
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