The tRNA-tufB operon in E. coli contains a total of five genes. Four of these encode tRNA molecules, while the final one encodes an elongation factor used in bacterial translation. The operon is regulated in two ways. It can be activated by the DNA-binding protein Fis, which binds upstream of the operon promoter and it increases gene transcription by altering the chromatin structure, making it easier for RNA polymerase to bind. The operon can also be negatively regulated by guanosine 3'-diphosphate 5-'triphosphate (ppgpp), a compound that is produced in E. coli in response to stress. ppgpp binds to the promoter region of the operon and inhibits transcription from occurring. The first four genes, thrU, tyrU, glyT and thrT are all transcribed into tRNA molecules. thrU and thrT are both threonine tRNAs with different anticodons (UGU and GGU), while tyrU is a tyrosine tRNA with the anticodin GUA, and glyT is a glycine tRNA with the anticodin UCC. The fifth gene in the operon, tufB, encodes the elongation factor Tu 2 protein. This protein binds the activated tRNAs in the ribosome, allowing for transcription to take place, and as such it is necessary for cell growth and function.

Operon: Elongation Factor References