Question

1. Ribosomal proteins that can act as translational repressors:

   		are not encoded by the same mRNA that they repress.
   		bind to a site on the mRNA near the start site of one gene in the operon.
   		bind to mRNA with higher affinity than to the appropriate rRNA molecule.
   		bind to the mRNA when sensing that levels of r-protein are low relative to rRNA.

Answer 1

For taking one example like S4 & S7 ribosomal proteins in E.coli they function like feedback repressors. that means they inhibit the translation  of thier own mRNA

Usually repressors are proteins they bind to transcriptional binding sites on DNA . These sites usually present on upstream of promoters .

When these repressors binds to upstream of promotor they change the strutural confirmation of the DNA so that the enzyme RNA POLYMERASE no longer able to bind to promoter,so that the translation of that particular mRNA will be hampered and gets inhibited.

In Feedback mechanism, when r- protein is high , in a cell if the sufficient levels are there then these ribosomal repressors will inhibit the r- protein mRNA translation,so that there is no longer synthesis of r- protein.