A cis-acting translational mutation in the beginning of the glnS gene was analyzed; this mutation creates a extra base pair to a proposed extended ribosome binding site. When increasing the complementarity to this extended ribosome binding site, it was demonstrated that the expression increased; correspondingly, when complementarity was decreasd the expression went down. It was also shown that the presence of rare codons near the beginning of the gene can affect expression.

Studies of a S13 mutant (rpsM413) revealed that the mutant allele is associated with slow growth rate and slow elongation rate. The 30S subunit showed a reduced sedimentation coefficient but was able to form apparently normal 70S ribosomes.

Investigations to see whether ribosomal mutants are able to affect proofreading in vivo found that the missense and nonsense suppressors are affected by rpsD mutations in a rather unpredictable manner. It was shown that the ribosome allele, the nature of the suppressor tRNA, the codon context, and the structure of the anticodon loop are the determinig factors. rpsL mutations decrease the nonsense suppression, in accordance with their restrictive effect on translational error formation.

Streptomycin, which is known to increase translational error in vitro, did not increase efficiency of nonsense suppressor tRNAs in strains with normal or rpsL ribosomes. It did so only in combination with one rpsL mutation which is associated with streptomycin pseudodependence.

The presence or absence of the modification ms2i6A37 in the tRNA was found to be a determining factor in the functional response to the ribosomal mutations. These effects strongly indicate that tRNA is directly involved in this phenomena.

The role of ppGpp was investigated, and the results suggest that it affects transcription efficiency, but not translation. ppGpp seems to play a role in the tuning of the coupling between transcription and translation.