Potentially Prebiotic Synthesis of Aminoacyl-RNA via a Bridging Phosphoramidate-Ester Intermediate - PubMed (original) (raw)
Potentially Prebiotic Synthesis of Aminoacyl-RNA via a Bridging Phosphoramidate-Ester Intermediate
Samuel J Roberts et al. J Am Chem Soc. 2022.
Abstract
Translation according to the genetic code is made possible by selectivity both in aminoacylation of tRNA and in anticodon/codon recognition. In extant biology, tRNAs are selectively aminoacylated by enzymes using high-energy intermediates, but how this might have been achieved prior to the advent of protein synthesis has been a largely unanswered question in prebiotic chemistry. We have now elucidated a novel, prebiotically plausible stereoselective aminoacyl-RNA synthesis, which starts from RNA-amino acid phosphoramidates and proceeds via phosphoramidate-ester intermediates that subsequently undergo conversion to aminoacyl-esters by mild acid hydrolysis. The chemistry avoids the intermediacy of high-energy mixed carboxy-phosphate anhydrides and is greatly favored under eutectic conditions, which also potentially allow for the requisite pH fluctuation through the variable solubility of CO2 in solid/liquid water.
Conflict of interest statement
The authors declare no competing financial interest.
Figures
Scheme 1. (A) Chemical Structures of RNA-Amino Acid Hybrid Compounds; (B) Reaction Scheme for the Formation of Aminoacyl-RNA Esters
RNA-amino acid phosphoramidate-ester (middle structure, 4) is formed from RNA phosphoramidate (2, left) and ester acceptor RNA (3) under activation conditions. The phosphoramidate bond can then be cleaved under mild acid conditions generating aminoacyl-RNA (5, right).
Figure 1
Room-temperature yields for formation of phosphoramidate-esters 4 via a nicked loop and 7-Leu via a nicked duplex. Bars are mean values based on three replicates. Each replicate is represented by a circular/triangular data point. Red hashed bars represent
l
-amino acid stereochemistry and blue checkered bars
d
- amino acid (where appropriate).
Figure 2
Eutectic yields for formation of phosphoramidate-esters 4 via a nicked loop and 7-Leu via a nicked duplex. Each replicate is represented by a circular/triangular data point. Red hashed bars represent
l
-amino acid stereochemistry and blue checkered bars
d
-amino acid (where appropriate). Darker colors indicate longer reaction times.
Figure 3
Top—Mechanism of hydrolysis of the phosphoramidate-ester 4 at pH = 3. The majority of 4 undergo phosphoramidate bond hydrolysis giving 5′-phosphoryl-5-mer 6 and the desired aminoacyl-10-mer 5 product, which can then degrade slowly back to template 3. Minority hydrolyses at the ester bond of 4 gives 3 and 5′ phosphoramidate-5-mer 2. Phosphoramidate 2 degrades either by direct hydrolysis to 5′-phosphoryl-5-mer 6, or by intramolecular oligonucleotide dephosphorylation to the 5′-hydroxyl-5-mer 9 in an amino acid-specific fashion. Bottom—Yields of formation of aminoacyl-10-mer 5 from phosphoramidate-ester 4 with different amino acids. aEstimate due to unknown products of hydrolysis. A discussion of the differing yields of Arg, Pro, and Ser is presented in the ESI.
References
- Liu Z.; Hanson C.; Ajram G.; Boiteau L.; Rossi J. C.; Danger G.; Pascal R. 5 (4H)-Oxazolones as effective aminoacylation reagents for the 3′-terminus of RNA. Synlett 2017, 28, 73–77. 10.1055/s-0036-1588647. -DOI
Publication types
MeSH terms
Substances
LinkOut - more resources
Full Text Sources