Some of these molecular fossils can, when located in RNA, "adorn" themselves with individual amino acids or even small chains of them ( peptides), according to Carell. The Carell group has now discovered that these non-canonical nucleosides are the key ingredient, as it were, that allows the RNA world to link up with the world of proteins.
It is highly probable that they are relicts of the former RNA world. We currently have knowledge of more than 120 such modified RNA nucleosides, which nature incorporates into RNA molecules. These non-information-coding nucleotides are very important for the functioning of RNA molecules. In addition to the four canonical bases A, C, G, and U, which encode genetic information, it also contains non-canonical bases, some of which have very unusual structures. In itself, RNA is a complicated macromolecule. To understand, we must take another, closer look at RNA. As laid out in a new paper published in Nature, Carell's working group has discovered a way in which this linking could have occurred. Furthermore, it is not clear how the linking of RNA molecules with the world of proteins could have come about, for which the genetic material, as we know, supplies the blueprints. For example, RNS is a very fragile molecule, especially when it gets longer. However, the hypothesis is not without its issues. Genetic material, as we understand it today, is made up of double strands of DNA, a slightly modified, durable form of macromolecule composed of nucleotides. "The RNA world idea has the big advantage that it sketches out a pathway whereby complex biomolecules such as nucleic acids with optimized catalytic and, at the same time, information-coding properties can emerge," says LMU chemist Thomas Carell. In the course of evolution, this replication could have improved and at some stage yielded more complex life. Only two nucleotides fit together in each case, meaning that one strand is the exact counterpart of another and thus forms the template for another strand. These so-called oligonucleotides were already capable of encoding small amounts of genetic information.Īs such single-stranded RNA molecules could also combine into double strands, however, this gave rise to the theoretical possibility that the molecules could replicate themselves-i.e. The hypothesis holds that nucleotides-the basic building blocks of the nucleic acids A, C, G, and U-emerged out of the primordial soup, and that short RNA molecules then formed out of the nucleotides.
Which conditions must have prevailed for the basic building blocks of more complex life to form? One of the main answers is based upon the so-called RNA world idea, which molecular biology pioneer Walter Gilbert formulated in 1986. Investigating the question as to how life could emerge long ago on the early Earth is one of the most fascinating challenges for science.
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