After the trace of the first molecule of life

2001/03/05 Roa Zubia, Guillermo - Elhuyar Zientzia

• Biokimika
• Biologia

In the last fifty years important efforts have been made to understand the molecular effect of life. It is now clear which components are involved. In general, the main ones are nucleic acids (DNA and RNA) and proteins.

The DNA molecule encodes information to make proteins. DNA is stored in the nuclei of cells and organelles that produce proteins, ribosomes, in the cytoplasm. The transport mediator is the RNA molecule. Although DNA research has been the most influential in the media lately, scientists are surprised by what they are learning about the RNA molecule. In short, the RNA, rather than mere mediation capacity, has been found to be able to catalyze chemical reactions. It is a data of great importance since until recently this capacity was only attributed to proteins.

Catalysts are essential for, among other things, copying molecules. This is therefore a definition of life from the biochemical point of view. Because of the ability of RNA to perform this work, suspicions that may be the first molecule of life have been strengthened.

Ribosomes, organelles that produce proteins, are made up of proteins and RNA. Amino acids to make proteins must be transported individually to the ribosomes to form chains. This task is also the responsibility of a type of RNA, RNA transfer (tRNA). In the structure of the tRNA there are two important zones, the so-called "minihelix" that binds the amino acid to the ribosome RNA.

The biochemists Koji Tamura and Paul Schimmel have synthesized a substitute for the tRNA molecule, which only has these two nuclei, and have joined another alternative molecule to ribosome (puromycin), in order to study its ability to form protein chains. The answer has been yes, that is, the mixture can bind amino acids, but with one condition. In the middle there must be imidazole molecules to help you.

Scientists are right to think that the first steps of living imidazole also existed, but there is no possibility of fully asserting. There are many pathways between amino acids, but RNA catalisis offers numerous advantages for life development. One of the most important is the possibility of making selective links between the junction of the tRNA minihelix.