How life arose on Earth: the secret of the appearance of proteins in the world of RNA is revealed

Earlier we said that at the originsThe origin of life on Earth was the so-called world of RNA. Scientists suggest that RNA components could have been brought to our planet with meteorites. Recall that ribonucleic acids are able to store information and copy it, that is, they can reproduce themselves. At the same time, mutations are possible during the copying process, which can be both harmful and beneficial. Moreover, unlike DNA, RNA can reproduce itself on its own, without the help of enzyme proteins. But the question remains, how did proteins originate? After all, information about proteins is encoded in DNA, but there has not yet been deoxyribonucleic acid in the world of RNA. The answer to this question was given by the staff of the University of Munich.

Scientists have figured out how RNA could synthesize the first proteins

How are proteins synthesized in cells

As we have already said, RNA consists of fivenitrogenous bases, or genetic letters - adenine (A), thymine (T), guanine (G), cytosine (C) and uracil (U). However, sometimes RNA contains chemical modifications of certain letters. In particular, in this form they are contained in nucleic acid chains in ribosomes.

Remember that ribosomes arereal factories in the cells of living organisms that synthesize protein. In general, ribosomes are a very complex mechanism, but they are based on RNA, which contain many ribosomal proteins.

Ribosomes are factories in living cells that synthesize proteins.

To create new proteins, ribosomes takeinformation from messenger RNA, or mRNA. They literally "scan" the mRNA to read the sequence of letters that code for the protein. But information alone is not enough to create a protein. The material from which they are synthesized is also required. These materials are amino acids. They are delivered to the ribosomes by transfer RNAs, or tRNAs.

As a result, the process of protein synthesis looks likeas follows - tRNA with a certain amino acid comes into contact with the mRNA site. If the ribosome finds the right tRNA with the right amino acid, it uses the last one in the protein chain. An important role in this process is played by modified letters, which contribute to a stable interaction between tRNA and mRNA.

How did squirrels appear on Earth?

We looked at how proteins are synthesized inribosomes. But how could they have arisen before the appearance of ribosomes? Previously, scientists have found that RNA with modifications can be synthesized from inorganic material. In addition, it is known that the modified letters are able to combine with amino acids.

Now, in a new study published inIn Nature, scientists have shown how modified RNAs are capable of making small proteins from amino acids on their own. To do this, the authors of the work synthesized RNA with modified letters and placed it in a solution with amino acids.

The first peptides could be created by RNA without the help of proteins

Artificially created RNA turned out to be smalland couples. What does this mean? Some genetic letters are able to connect with each other by hydrogen bonds. For example, adenine can combine with thymine or uracil. Guanine can be combined with cytosine. Such pairs are called complementary to each other.

As a result, two nucleic acids or eventwo sections of the same RNA can connect to each other if the sequence of letters facilitates this. Such RNAs are usually called complementary to each other.

In their work, scientists used one RNA withwith a modified A on the end, and the other with a modified Y. When the two RNAs joined, the letters A and Y ended up next to each other. At the same time, the amino acid switched from the donor letter A to the acceptor letter Y.

IMPORTANT! We are waiting for all our readers on the Yandex.Zen channel, where we publish important and interesting information. Subscribe so you don't miss out.

Then the scientists began to heat the molecules, as a resultcausing the RNA to separate. But when the molecules began to cool, they again approached. At the same time, an RNA donor was connected to the acceptor RNA, which contained a new amino acid on the letter A. The latter eventually also switched to an acceptor letter. As a result, the letter A already contained two amino acids. Thus, the number of amino acids per letter could be increased to fifteen. Thus, a small peptide (a protein formed by amino acids) arises even without a ribosome, but only through the interaction of two RNAs.

The genetic code could have arisen as a result of the interaction of RNA and proteins

How did the complex genetic code originate?

From the foregoing, it follows that RNA,being in the same solution with amino acids, could well combine them into peptides. Moreover, the proteins formed on the modified letters strengthened the bond between the interacting RNAs. In other words, nucleic acids could create proteins, which, in turn, directed the development of RNA along a certain path. For example, they could help increase their length.

Of course, this is not yet a genetic code, but withover time, certain RNAs with a characteristic sequence of letters could arise that synthesized proteins with a certain amino acid composition. Gradually, these molecules evolved, resulting in complex enzymatic mechanisms and a true genetic code.

Of course, protein-synthesizing RNA, and even DNA, is not yet life. According to some scientists, life could have arisen from a hybrid of DNA and RNA molecules. How this happened can be found here.