How life can emerge from inanimate matter is one of the grand questions in science. Self-replicating molecules are necessary for the transition from chemistry to biology, but they need to acquire additional functions for life to emerge. Catalysis is one of the most essential of such functionalities, but mechanisms through which self-replicators can acquire catalytic and, in extension, metabolic properties have remained elusive. Here we show how catalytic activity and promiscuity in a self-replicator emerges through co-option: features that are selected to benefit replication inadvertently result in an arrangement of chemical functionalities that is conducive to catalysis. Specifically, we report self-assembly driven self-replicators that promote both a model retro-aldol reaction and the cleavage of fluorenylmethoxycarbonyl groups, with the latter transformation exerting a positive feedback on replication (protometabolism). Such chance invention of new function at the molecular level marks a pivotal step toward the de novo synthesis of life.
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Data for Figs. 2 and 3 and Extended Data Figs. 1–3 and 5 are available as source data with this paper. All other data are available from the corresponding author on request.
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RStudio Team (RStudio Inc., 2015); https://www.rstudio.com
We gratefully acknowledge a Marie Skłodowska Curie Individual Fellowship (project no. 751509) to C.M. and funding from the Netherlands Organisation for Scientific Research (NWO, Veni grant no. 722.017.007 to C.M., Vici grant no. 724.012.002 to S.O.), as well as support from the ERC, COST (CM1304) and the Dutch Ministry of Education, Culture and Science (Gravitation programme 024.001.035).
The authors declare no competing interests.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Comparison of the reaction progress between the uncatalyzed retro-aldol reaction (red in a and b) and that in the presence of different concentration of 1 (a) and varying concentrations of a mixture of 13/14 (b). (c): Reaction progress monitored spectrophotometrically with 16 (25 μM) and methodol (600 μM, in triplicates with single standard deviation shown as shaded area). Red and blue dotted lines are linear fits for the observed burst (first 20 minutes) and steady state rate (100–200 minutes). (d): Apparent catalytic efficiencies for the cleavage of methodol (200 μM) of 16 and replicators featuring lysine-to-arginine mutations. Source data
(a) pH titration for 1 and 16 fibres in water (both in duplicates). The buffering capacity of monomers at a pH between 5 and 7 can be attributed to the presence of aromatic thiols in 1. In contrast, 16 fibres do not reveal appreciable levels of an ionizable group in the range from 5–8. The absence of a recognisable plateau at the apparent pKa of the lysines active in the retro-aldol (pKa,app = 7.4; Fig. 2e) or FMOC-glycine cleavage reactions (pKa,app = 7.1; Extended data Fig. 5a) indicates that, for each of these reactions, the fraction of lysine residues in the fibres that are catalytically active is low. All error bars shown correspond to a single standard deviation. (b-c) TEM images of 16 fibres at low and high pH regimes do not show a change in morphology. Source data
Extended Data Fig. 3 Emergence of catalytic activity of the retro-aldol reaction in a stirred sample of 1 correlates with fibre formation.
(a): Rate of formation of retro-aldol product 3 over the course of the experiments. Solid line represents a linear fit to the uncatalyzed reaction. (b–d): Concentration of 16 (b), 1 (c), and 14 (d) followed over time. Colour code as indicated in the legend. Source data
For agitated samples (a–f) fibres become detectable after 8.5 hours, which correlates with the increase in the concentration of 16 in the experiment shown in Fig. 2. Neither the non-agitated sample (g, h) nor the sample lacking 1 (i) showed detectable levels of fibres after 48 hours.
Extended Data Fig. 5 Emergence of catalytic activity of FMOC cleavage in a stirred sample of 1 correlates with fibre formation and an increase in the oxidation rate.
(a), pH rate profile for the cleavage of FMOC-glycine (100 μM) catalysed by replicator 16 (40 μM in 1). (b), Apparent catalytic efficiencies for the cleavage of FMOC glycine (200 μM) by 16 and replicators featuring lysine-to-arginine mutations. (c), Data for experiments as shown in Fig. 3b, but using 200 μM FMOC-glycine. The emergence of 16 (dark blue circles) coincides with the onset of FMOC-glycine cleavage (red circles) and 16 replicates faster when compared to a sample that does not contain FMOC-glycine (light blue circles). (d), A comparison of oxidation rates in the same experiment showed an up to 4.7 fold increase (purple arrow) once 5 is liberated, providing further evidence for the positive feedback loop shown in Fig. 3b. (e), A comparison of the oxidation of 1 (100 μM) in presence (red circles) and absence (blue circles) of 5 (100 μM) confirmed that this FMOC-cleavage product is responsible for enhancing the rate of oxidation of 1. Experiments were performed in borate buffer pH 8.1, containing 5% acetonitrile at 40 °C. All error bars shown correspond to a single standard deviation. Source data
UPLC and UV data of the retro-aldol reaction, pH rate profile of the retro-aldol reaction.
UPLC data of the FMOC deprotection reaction.
UPLC and UV data for the kinetic characterization of 1, 13/14 and other replicators. Includes UPLC calibration.
pH titration data.
UPLC data of the emergence experiment with methodol including UPLC calibrations.
pH rate profile for the cleavage of FMOC-glycine, catalytic efficiencies of various replicators towards FMOC-glycine cleavage, UPLC data for emergence experiments with FMOC-glycine and measurements of oxidation of building block 1 with and without DBF. Also includes UPLC calibration and the determination of the extinction coefficient.
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Ottelé, J., Hussain, A.S., Mayer, C. et al. Chance emergence of catalytic activity and promiscuity in a self-replicator. Nat Catal (2020). https://doi.org/10.1038/s41929-020-0463-8
Nature Reviews Chemistry (2020)