Translation initiation is the most important step within a series of protein biosynthesis processes because the incorporation of ribosomes to a mRNA mainly determines efficiencies of translation. In bacteria, translation enhancers located on the 5' upstream of the Shine-Dargalno (SD) sequence on mRNAs are known to accelerate the efficiency of protein biosynthesis. To investigate the role of translation enhancers in translation initiation, we analyzed binding kinetics of a 30S ribosomal subunit to a mRNA immobilized on a 27 MHz quartz-crystal microbalance (QCM). The association constant (Ka) was rather low for the mRNA including a translation enhancer sequence compared with that for the mRNA without translation enhancers. These kinetic parameters suggest that translation enhancers destabilize the ribosome-mRNA complex on an SD sequence to move on the next step of decoding its mRNA.
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