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Competition between model protocells driven by an encapsulated catalyst

A Corrigendum to this article was published on 20 June 2013

This article has been updated


The advent of Darwinian evolution required the emergence of molecular mechanisms for the heritable variation of fitness. One model for such a system involves competing protocell populations, each consisting of a replicating genetic polymer within a replicating vesicle. In this model, each genetic polymer imparts a selective advantage to its protocell by, for example, coding for a catalyst that generates a useful metabolite. Here, we report a partial model of such nascent evolutionary traits in a system that consists of fatty-acid vesicles containing a dipeptide catalyst, which catalyses the formation of a second dipeptide. The newly formed dipeptide binds to vesicle membranes, which imparts enhanced affinity for fatty acids and thus promotes vesicle growth. The catalysed dipeptide synthesis proceeds with higher efficiency in vesicles than in free solution, which further enhances fitness. Our observations suggest that, in a replicating protocell with an RNA genome, ribozyme-catalysed peptide synthesis might have been sufficient to initiate Darwinian evolution.

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Figure 1: Schematic representation of adaptive changes and competition between protocell vesicles.
Figure 2: Ser-His catalysis in the presence of fatty-acid vesicles results in increased synthesis of the hydrophobic dipeptide product and decreased substrate hydrolysis.
Figure 3: Competition between vesicles with and without the hydrophobic dipeptide AcPheLeuNH2.
Figure 4: Competition between populations of protocell vesicles.
Figure 5: Inhibitory effect of salt and buffer on competitive growth of vesicles.
Figure 6: Vesicle growth and division.
Figure 7: Transmembrane pH gradient generated by growth of vesicles during competitive micelle uptake.

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Change history

  • 03 June 2013

    In the version of this Article originally published, in Fig 3a, the description for the open triangle should have read: '1 equiv. dye-labelled empty vesicles + vesicles without dipeptide'. This has been corrected in the HTML and PDF versions of the Article.


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J.W.S. is an Investigator of the Howard Hughes Medical Institute. This work was supported in part by National Aeronautics and Space Administration Exobiology grant NNX07AJ09G. We thank A. Engelhart, C. Hentrich, I. Budin and R. Wieczorek for discussions and help with manuscript preparation.

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Both authors contributed to the design of the experiments and to writing the paper. Experiments were conducted by K.A.

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Correspondence to Jack W. Szostak.

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The authors declare no competing financial interests.

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Adamala, K., Szostak, J. Competition between model protocells driven by an encapsulated catalyst. Nature Chem 5, 495–501 (2013).

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