The newly described chemical reactions could have assembled DNA building blocks before life forms and their enzymes existed.
The discovery promotes the theory that life on our planet originated from a combination of RNA and DNA.
The chemists at Scripps Research have made a discovery that supports a surprisingly new view of how life originated on our planet.
In a study published in the journal Chemistry Engandte Chemi, They showed that a simple compound called diamidophosphate (DAP), which was reasonably present on Earth before life took place, could be chemically knitted together into smaller ones. DNA The building blocks that are called deoxynucleotides are called the strands of primitive DNA.
Discovery is the latest in a series of discoveries for the last several years, DNA. And his closest chemical cousin RNA Emerged simultaneously as products of similar chemical reactions, and that is, the first life forms on Earth – the first self-replicating molecules were a combination of both.
This discovery may also lead to new practical applications in chemistry and biology, but its main significance is that it addresses the age-old question of how life originated on Earth. In particular, how it replicates self-replicating DNA-RNA. The combination paves the way for a more comprehensive study of what could have evolved on primitive Earth and ultimately the more mature biology of modern organisms.
“This discovery is an important step towards the development of a detailed chemical model of how first life is formed on Earth,” says Ramanarayana Krishnamurthy, senior professor of chemistry and associate professor of chemistry at Scripps Research.
These findings also push the field of life chemistry based on it in recent decades, which has dominated it: “RNA. The World ”hypothesis shows that the first replicas were made of RNA. Were based, and DNA. Emerged only after production. RNA is a form of life.
What is RNA? Too sticky?
Krishnamurthy and others have questioned the RNA World hypothesis in part because RNA molecules can be too “sticky” to serve only as first self-replicators.
One strand of RNA can attract other individual RNA building blocks, clinging to it to form a kind of mirror-image strand – each building block in the new strand binds its complementary building block to the original, “template” strand. If the new strand can be separated from the sample strand, and by the same process, begin to template other new strands, then it achieves the feat of self-replication that subjugates life.
But while RNA strands may be good at templating complementary strands, they are not as good at separating from these strands. Modern organisms make enzymes that bind to RNA. Or DNA – twins can force strands to move in different ways, thus enabling replication, but it is unclear how this could have happened in a world where these enzymes did not yet exist.
Chimeric workround
Recent studies by Krishnamurti and colleagues have shown that “chimeric” molecular strands which are part DNA and part RNA can cope with this problem, as they can sample complementary strands in a less-sticky way that allows them to separate relatively easily. .
Chemists have also shown in papers widely cited over the past few years that RNA and DNA, simple ribunucleoside and deoxynucleoside building blocks, respectively, can occur in very similar chemical conditions on early Earth.
Moreover, in 2017 they reported that the organic compound DAP would have played a crucial role in modifying the ribonucleosides and drawing them together in the first RNA strands. A new study shows that DAP would have done the same for DNA under similar conditions.
“We are surprised that the use of DAP to react with deoxynucleotides works better when deoxynucleotides are not all the same, but instead a combination of different DNA‘ characters ’like D and N, or G and C, Says Eddie Jimenez, the first author of a postdoctoral research associate, PhD at Krishnamurti Lab.
“Now that we better understand how primitive chemistry may have created the first RNA and DNA, we can use it on a combination of ribunucleoside and deoxynucleoside building blocks to understand how chimeric molecules form – and that And whether it can be developed. Says Krishnamurti.
He notes that the work may also have a wide range of practical applications. Synthesis of DNA and RNA – for example in the “PCR” technique COVID-19 Tests – Similar to the vast global business, but based on enzymes that are relatively fragile and therefore have many limitations. Krishnamurti says strong, enzyme-free chemical methods for making DNA and RNA can be more attractive in many respects.
Reference: “Prebiotic phosphorylation and component oligomerization of deoxynucleotides to form DNA” by Eddie Jimenez, Cl ,mantine Gibbard and Ramannarayan Krishnamurthy, 15 December 2020 Engandte Chemi.
DOI: 10.1002 / anie.202015910
Funded by the Simmons Foundation.
