The accuracy of Qβ RNA translation 2. Errors during the synthesis of Qβ proteins by cell-free <em>Escherichia coli</em> extracts.

The accuracy of Qβ translation by Escherichia coli extracts in polymix and a conventional Tris/Mg²⁺ system has been followed. Misinsertions of histidine and of tryptophan into the phage coat protein were less frequent in polymix than in Tris/Mg²⁺, as were errors leading to u change in the coat protein pI. Even the lowest Qβ error rates, however, were still an order of magnitude greater than those for poly(U) or poly(U-G) translation. Comparing Qβ translational errors made in vitro to those found in whole cells, histidine misinsertions were almost twice as frequent, errors leading to a coat protein charge change six times more frequent and tryptophan misinsertions at least 15 times more frequent in vitro. The relation of these findings to measurements of translational accuracy and to factors affecting fidelity is discussed. [ABSTRACT FROM AUTHOR]