Effect of E. coli ribosomal protein S1 on the fidelity of the translational elongation step: reading and misreading of poly(U) and poly(dT).

Ribosomal protein S1 was selectively removed from E. coli ribosomes by affinity chromatography and the effect of added S1 on the translation of poly(dT) [which is read as poly(U) in the presence of neomycin] and on the misreading of poly(U) and poly(dT) were examined. S1 enhances the translation of poly(dT) at low template concentration, which is similar to the effect of S1 on poly(U) translation. The misreading of poly(dT) by E. coli ribosomes is at a lower level than is the case with poly(U). This low misreading is the same for "S1-dependent" and "S1-independent" modes of translation. On the other hand, the misreading of poly(U) is significantly reduced when S1 is present. These results thus indicate that S1 not only facilitates the binding of mRNA to the ribosome as already known, but also plays a role in the correct codon-dependent selection of aminoacyl-tRNA.