Semi-artificial microorganisms - New breakthrough in molecular biology

Life on Earth appeared about 3.5 billion years ago and lasts until today with only 4 types of base molecules in the genetic code.

These bases - denoted by 4 letters G, C, A and T - are present in DNA molecules and used by every living organism to guide protein synthesis. However, scientists at the Scripps Research Institute (TSRI), the United States have designed a bacterium that can integrate 2 types of base molecules not found in nature (artificial bases) - yes named X and Y - into the genome that contains four natural bases above to encode proteins.

Cells can translate base codes to make proteins

This semi-artificial E.coli strain (semi synthesis) is the first bacterium to contain new bases, and they can use these bases to encode the synthesis process. protein in cells. GS. Floyd Romesberg, the author of the study, cannot be called a new life form, but it is closest to a form of life that humans can create. This is also the first time a cell can translate proteins into proteins that use non-G, C, A and T. bases.

This research builds on previous attempts by Romesberg and colleagues to expand the types of bases that exist naturally in DNA molecules. If only 4 types of base G, C, A, and T are used, the creature can only encode 20 amino acids, whereas if 2 more bases are X and Y, the number of amino acids is encoded will reach 152.

Prof.omesberg and his colleagues have spent 20 years studying to achieve breakthrough achievements like today. In 2014, the team made a great leap forward in creating a microorganism capable of copying X and Y bases in its DNA molecule. A year earlier, they also discovered that this bacterium could store genetic information and pass it on to descendants in the process of cell division. However, it is not enough to store and inherit information through new bases, because to be really useful they need to be transcribed into RNA molecules and then translated into proteins.

Fluorescent cells represent a protein encoded by artificial bases in DNA molecules.

The team made an important step forward by integrating new bases into the genome that contains four natural bases. These genes are then transcribed into RNA molecules (which also contain new bases) and then this RNA molecule is used by the cell to guide the binding of new amino acids to protein molecules.

The protein molecule formed in the process is a variant of the green fluorescent protein (GFP) , a natural luminescent index commonly used in experiments. Genetics, and contains special non-existent amino acids in nature integrated in a pre-selected location.

Romesberg argues that this is only a very small transformation that humans can do with the natural way of life, but a pioneering transformation.

Redefining the role of hydrogen bonds

This study also showed for the first time that hydrogen bonds (thought to have a decisive role in DNA decoding) may not be as important as scientists previously thought. The team found that the binding forces other than hydrogen interaction can be involved multiple times in all steps of the process of storing and decoding genetic information.

These scientists have designed X and Y to be hydrophobic so that they can only be paired together without linking to natural bases, in order to keep them from randomly binding to A, T, C or G. And this turns out to suggest that the lack of additional hydrogen bonds will not affect the cell, because they found that X and Y can also be transcribed and translated successfully. .

Thus, the study's remarkable finding is not only that cells have the ability to transcription and translation of hydrophobic artificial bases, but also that they perform these two processes in a very effective way. . The purity of the desired translational amino acid to bind to the protein molecule reaches 98%, indicating that these artificial bases can smoothly integrate into the natural processes of the cell for coding. and decoding genetic information.

It is hoped that in the future, the results of this study will be used for the purpose of treatment.