Extraribosomal functions of ribosomal proteins.

The discovery of DNA-binding motifs in ribosomal proteins has led to the conjecture that the transition of the ribosome from an RNA to an RNP machine occurred by adding pre-existing proteins. Supportive, but circumstantial, evidence for the hypothesis is adduced from the finding that many ribosomal proteins have a second function apart from the particle. These extraribosomal functions are enumerated.