Nobel Prize Winner Cites the "Ingeniously Designed" Architecture of the Ribosome
In 2009, Israeli structural biologist Ada Yonath shared the Nobel Prize in Chemistry for her work on the structure and function of the ribosome. More recently, she had this to say about the "ingeniously designed" architecture of the ribosome:
Ribosomes, the key players in the translation process, are universal ribozymes performing two main tasks: decoding genetic information and polymerizing amino acids. Hundreds of thousands of ribosomes operate in each living cell due to the constant degradation of proteins through programmed cell death, which is matched by simultaneous production of proteins. For example, quickly replicating cells, e.g. liver cells, may contain a few million ribosomes. Even bacterial cells may contain [up] to 100,000 ribosomes during their log period. Other constituents are the mRNA chains, produced by the transcription of the segments of the DNA that should be translated, which carry the genetic information to the ribosomes, and tRNA molecules bring the cognate amino acids to the ribosome. To increase efficiency, a large number of ribosomes act simultaneously as polymerases, synthesizing proteins by one-at-a-time addition of amino acids to a growing peptide chain, while translocating along the mRNA template, and producing proteins on a continuous basis at an incredible speed, namely up to 20 peptide bonds per second.Yonath said much the same thing in her Nobel Prize acceptance lecture. Ultimately, Yonath is an evolutionist. But even evolutionists who are structural biologists can't deny the elegance of the ribosome.
Ribosomes are giant assemblies composed of many different proteins (r-proteins) and long ribosomal RNA (rRNA) chains. Among these, the RNA moieties perform the two ribosomal main functions. The ratio of rRNA to r-proteins (~2:1) is maintained throughout evolution, except in mitochondrial ribosome (mitoribosome) in which ~half of the bacterial rRNA is replaced by r-proteins. Nevertheless, the active regions are almost fully conserved in all species. In all organisms ribosomes are built of two subunits, which associate to form the functionally active ribosomes. In prokaryotes, the small subunit, denoted as 30S, contains an RNA chain (16S) of ~1500 nucleotides and ~20 different proteins. The large subunit (50S in prokaryotes) has two RNA chains (23S and 5S RNA) of about 3000 nucleotides in total, and different >31 proteins. The available three dimensional structures of the bacterial ribosome and their subunits show that in each of the two subunits the ribosomal proteins are entangled within the complex rRNA conformation, thus maintaining a striking dynamic architecture that is ingeniously designed for their functions: precise decoding; substrate mediated peptide-bond formation and efficient polymerase activity.
(See Ada Yonath, "Supervisor's Foreword," in Chen Davidovich, Targeting Functional Centers of the Ribosome, p. vii (Springer-Verlag, 2011) (emphasis added).)