Steric complementarity in the decoding center is important for tRNA selection by the ribosome.

ABSTRACT: Accurate tRNA selection by the ribosome is essential for the synthesis of functional proteins. Previous structural studies indicated that the ribosome distinguishes between cognate and near-cognate tRNAs by monitoring the geometry of the codon-anticodon helix in the decoding center using the universally conserved 16S ribosomal RNA bases G530, A1492 and A1493. These bases form hydrogen bonds with the 2'-hydroxyl groups of the codon-anticodon helix, which are expected to be disrupted with a near-cognate codon-anticodon helix. However, a recent structural study showed that G530, A1492 and A1493 form hydrogen bonds in a manner identical with that of both cognate and near-cognate codon-anticodon helices. To understand how the ribosome discriminates between cognate and near-cognate tRNAs, we made 2'-deoxynucleotide and 2'-fluoro substituted mRNAs, which disrupt the hydrogen bonds between the A site codon and G530, A1492 and A1493. Our results show that multiple 2'-deoxynucleotide substitutions in the mRNA substantially inhibit tRNA selection, whereas multiple 2'-fluoro substitutions in the mRNA have only modest effects on tRNA selection. Furthermore, the miscoding antibiotics paromomycin and streptomycin rescue the defects in tRNA selection with the multiple 2'-deoxynucleotide substituted mRNA. These results suggest that steric complementarity in the decoding center is more important than the hydrogen bonds between the A site codon and G530, A1492 and A1493 for tRNA selection.

SUBMITTER: Khade PK 

PROVIDER: S-EPMC3744617 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature