CH391L/S12/TranslationRBSandCodons
Translation
Translation is the third stage of protein synthesis and proceeds in four phases: activation, initiation, elongation and termination. Activation occurs when an amino acid is covalently bonded to a tRNA. Initiation follows when the ribosome binds to the 5' end of mRNA. This allows translation to build a particular protein. This process is halted once a stop codon (UAA, UAG, or UGA) is reached because no tRNA can bind to these codons. What does recognize this codon is a "release factor" protein that disassembles the ribosome/mRNA complex.
An illustration of this process is shown as follows:
Shown above is a ribosome translating a protein that is secreted into the endoplasmic reticulum. tRNAs are colored dark blue.
Bacterial Ribosome Binding Sites
A ribosome binding site (RBS) is a region 6-7 nucleotides upstream of the start codon AUG in prokaryotes called the Shine-Dalgarno sequence (5′–GGAGGU–3′). The ribosome will base pair with this site through its own rRNA as well at the start codon using tRNA. What makes this an interesting topic of research is the fact that the Shine-Dalgarno sequence is not the "optimal" RBS for all expression processes.
