TPP riboswitch
The TPP riboswitch, also known as the THI element and Thi-box riboswitch, is a highly conserved RNA secondary structure. It serves as a riboswitch[1][2] that binds thiamine pyrophosphate (TPP) directly and modulates gene expression through a variety of mechanisms in archaea, bacteria and eukaryotes.[3][4][5] TPP is the active form of thiamine (vitamin B1), an essential coenzyme synthesised by coupling of pyrimidine and thiazole moieties in bacteria. The THI element is an extension of a previously detected thiamin-regulatory element, the thi box, there is considerable variability in the predicted length and structures of the additional and facultative stem-loops represented in dark blue in the secondary structure diagram [6] Analysis of operon structures has identified a large number of new candidate thiamin-regulated genes, mostly transporters, in various prokaryotic organisms.[7] The x-ray crystal structure of the TPP riboswitch aptamer has been solved.[8] See alsoReferences
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