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  • Title: On the pH dependence of class-1 RF-dependent termination of mRNA translation.
    Author: Indrisiunaite G, Pavlov MY, Heurgué-Hamard V, Ehrenberg M.
    Journal: J Mol Biol; 2015 May 08; 427(9):1848-60. PubMed ID: 25619162.
    Abstract:
    We have studied the pH dependence of the rate of termination of bacterial protein synthesis catalyzed by a class-1 release factor (RF1 or RF2). We used a classical quench-flow technique and a newly developed stopped-flow technique that relies on the use of fluorescently labeled peptides. We found the termination rate to increase with increasing pH and, eventually, to saturate at about 70 s(-1) with an apparent pKa value of about 7.6. From our data, we suggest that class-1 RF termination is rate limited by the chemistry of ester bond hydrolysis at low pH and by a stop-codon-dependent and pH-independent conformational change of RFs at high pH. We propose that RF-dependent termination depends on the participation of a hydroxide ion rather than a water molecule in the hydrolysis of the ester bond between the P-site tRNA and its peptide chain. We provide a simple explanation for why the rate of termination saturated at high pH in our experiments but not in those of others.
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