Post 45: The ribosome is a ribozyme! 😱

In school, we are taught that the ribosome is responsible for synthesizing proteins. To illustrate this, easy-to-understand drawings are used to show that the ribosome is composed of RNA and proteins (about 50 in bacteria). However, this oversimplification may be downplaying the importance of RNA.

RNA is usually understood as the precursor to proteins. For this to happen, it has to be translated into amino acids by the ribosome. However, RNA by itself can also catalyze reactions just like proteins! When an RNA has this catalytic ability, we call it a ribozyme.

In reality, the ribosome is largely made up of ribozymes (rRNAs 5s, 16s, and 23s). The function of the ribosomal proteins is to provide structural support and to guide the rRNA to adopt structural conformations that are catalytic.

The remarkable structural plasticity of RNA, as well as its catalytic ability, are the foundations of the RNA world hypothesis, which suggests that before DNA and proteins existed, RNA molecules served as carriers of genetic information. rRNA is not the only ribozyme; thanks to bioinformatics, another 14 ribozymes capable of performing different catalytic reactions have been detected.

Refs:

1. The Ribosome Is a Ribozyme
2. To learn more about the role of ribozimes in the evolution: Promiscuous Ribozymes and Their Proposed Role in Prebiotic Evolution
3. An example of how to detect ribozimes with bioinformatics: A widespread self-cleaving ribozyme class is revealed by bioinformatics