Substrate-assisted catalysis of peptide bond formation by the ribosome |
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Authors: | Weinger Joshua S Parnell K Mark Dorner Silke Green Rachel Strobel Scott A |
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Affiliation: | Department of Molecular Biophysics and Biochemistry, Yale University, 260 Whitney Avenue, New Haven, Connecticut 06520-8114, USA. |
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Abstract: | The ribosome accelerates the rate of peptide bond formation by at least 10(7)-fold, but the catalytic mechanism remains controversial. Here we report evidence that a functional group on one of the tRNA substrates plays an essential catalytic role in the reaction. Substitution of the P-site tRNA A76 2' OH with 2' H or 2' F results in at least a 10(6)-fold reduction in the rate of peptide bond formation, but does not affect binding of the modified substrates. Such substrate-assisted catalysis is relatively uncommon among modern protein enzymes, but it is a property predicted to be essential for the evolution of enzymatic function. These results suggest that substrate assistance has been retained as a catalytic strategy during the evolution of the prebiotic peptidyl transferase center into the modern ribosome. |
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