The discoveries concerning the unique abiotic chemistry of ATP apparently hasn’t stopped.
I previously posted about the discovery that abiotic chemistry can explain why ATP has the unique role it does in cellular metabolism.
Nick Lane’s research group as UCL has found an answer to one of the most fundamental mysteries about the chemistry of life: Why do cells use ATP rather than any one of the other, equally capable nucleotide triphosphates? It turns out the answer is found uniquely in abiotic chemistry.
The ion Fe3+ will catalyze the phosphorylation of only ADP to ATP with acetyl-phosphate(AcP) under mild and anoxic conditions in water, whereas the reaction does not occur for any of the other nucleotides, and no other common ion or metabolic cofactor seems able to catalyze the reaction.
That, however, raised an interesting question and potential problem with the emergence of RNA. If only ADP can be phosphorylated to ATP through abiotic chemistry (not aided by enzymes), and none of the other NDPs can, how do you get the other NTPs (GTP, CTP, and UTP) for participation in RNA polymers, for example? And what use, if any, would ADP or ATP have?
Turns out the adenine moiety of adenosine is again unique in that it can act as a sort of catalyst (and none of the other nucleosides can do this reaction), and the other nucleoside diphosphates can be phosphorylated to NTPs by ADP+AcP, with Fe3+ or Al3+ ions. So even initially ADP has a function, in that it can help produce the missing GTP, CTP, and UTP.
Under enzyme catalysis, adenosine triphosphate (ATP) transfers a phosphoryl group to canonical ribonucleotide diphosphates (NDPs) to form ribonucleotide triphosphates (NTPs), the direct biosynthetic precursors to RNA. However, it remains unclear whether the phosphorylation of NDPs could have occurred in water before enzymes existed and why an adenosine derivative, rather than another canonical NTP, typically performs this function. Here, we show that adenosine diphosphate (ADP) in the presence of Fe3+ or Al3+ promotes phosphoryl transfer from acetyl phosphate to all canonical NDPs to produce their corresponding NTP in water at room temperature and in the absence of enzymes. No other NDPs were found to promote phosphorylation, giving insight into why adenosine derivatives specifically became used for this purpose in biology. The metal-ADP complexes also promote phosphoryl transfer to ribonucleoside monophosphates (NMPs) to form a mixture of the corresponding NDPs and NTPs, albeit less efficiently. This work represents a rare example in which a single nucleotide carries out a function critical to biology without enzymes. ADP-metal complexes may have played an important role in nucleotide phosphorylation in prebiotic chemistry.
Is that more of that supposedly non-existing progress in origin of life research?