Decoding errors and the involvement of the E-site.

Life depends on the faithful translation of the genetic information into proteins. Ribosomes have developed remarkable mechanisms to ensure the accurate synthesis of proteins. In the first part of this review various types of ribosomal errors and their importance for cell-life are surveyed, while in the second part two important aspects of the ribosomal E-site for the accuracy of translation are considered: (i) The fact that usually misincorporations are not harmful for the cell, since only one in about 400 misincorporations will affect the structure and/or function of a protein, is a function of the E-site. (ii) In contrast, an extremely harmful translational error is a loss of the reading frame, resulting in an immediate loss of the genetic information. Maintenance of the reading frame is one of the most remarkable achievements of the ribosome; only once in about 30,000 elongation cycles is the reading frame lost. A cognate tRNA at the E-site is an essential prerequisite for this high precision.