Question

Explain how synthesis of ribosomal proteins in E. coli is regulated at the level of translation.

Answer 1

Answer: The synthesis of ribosomal proteins (r-protein) in Escherichia coli is regulated at the level of translation. The rate of synthesis of r-protein is proportional to the square of the bacterial growth rate. Transcription and translation are coordinately controlled. The number of r-protein operons in E. coli is 19. The ribosomal protein genes are clustered with other r-proteins genes or with the proteins involved in translation. The translational regulation of r-proteins depends on the binding of the r-protein to a single site. The regulation of r-protein genes is coupled. That means the translation of a particular r-protein gene requires the prior translation of the gene immediately upstream to it. The control is through an autogenous feedback mechanism. Likewise, the synthesis of all of the ribosomal components is coregulated. The r-protein not only binds specifically to its rRNA but also the operator site of its mRNA. When there is excess production of r-proteins, the r-proteins bind the operator and inhibits translation. Repressor r-protein not only reduces translation initiation but also degrades the mRNA.