A riboswitch mechanism regulating translation of mRNA

(a) TPP is produced by translation of E. coli thiMD mRNA at low TPP concentration. (b) At high TPP concentration, translation is inhibited by TPP binding to riboswitch sequences(a) TPP is produced by translation of E. coli thiMD mRNA at low TPP concentration. (b) At high TPP concentration, translation is inhibited by TPP binding to riboswitch sequences

(a) Low TPP: Riboswitch not active (b) High TPP: Riboswitch active Riboswitch sequences Shine—Dalgarno sequestor stem loop mRNA 5' «:1 mRNA 9d b —>Translation is inhibited. Shine—Dalgarno antisequestor stem loop Low TPP generates formation of At high TPP concentration, TPP binds Shine—Dalgarno antisequestration riboswitch to sequester the Shine—Dalgarno stem loop that permits thiMD sequence and initiator codon, inhibiting operon gene translation. translation.