Current theories on the origin of life reveal significant gaps in our understanding of the mechanisms that allowed simple chemical precursors to coalesce into the complex polymers that are needed to sustain life. The volcanic gas carbonyl sulfide (COS) is known to catalyze the condensation of amino acids under aqueous conditions, but the reported di-, tri-, and tetra-peptides are too short to support a regular tertiary structure. Here, we demonstrate that alanine and valine, two of the proteinogenic amino acids believed to have been among the most abundant on a prebiotic earth, can polymerize into peptides and subsequently assemble into ordered amyloid fibers comprising a cross-β-sheet quaternary structure following COS-activated continuous polymerization of as little as 1 mm amino acid. Furthermore, this spontaneous assembly is not limited to pure amino acids, since mixtures of glycine, alanine, aspartate, and valine yield similar structures.

Enzymes are capable of directing complex stereospecific transformations and of accelerating reaction rates many orders of magnitude. As even the simplest known enzymes comprise thousands of atoms, the question arises as to how such exquisite catalysts evolved. A logical predecessor would be shorter peptides, but they lack the defined structure and size that are apparently necessary for enzyme functions. However, some very short peptides are able to assemble into amyloids, thereby forming a well-defined tertiary structure called the cross-β-sheet, which bestows unique properties upon the peptides. We have hypothesized that amyloids could have been the catalytically active precursor to modern enzymes. To test this hypothesis, we designed an amyloid peptide library that could be screened for catalytic activity. Our approach, amenable to high-throughput methodologies, allowed us to find several peptides and peptide mixtures that form amyloids with esterase activity. These results indicate that amyloids, with their stability in a wide range of conditions and their potential as catalysts with low sequence specificity, would indeed be fitting precursors to modern enzymes. Furthermore, our approach can be efficiently expanded upon in library size, screening conditions, and target activity to yield novel amyloid catalysts with potential applications in aqueous-organic mixtures, at high temperature and in other extreme conditions that could be advantageous for industrial applications.

The prebiotic replication of information-coding molecules is a central problem concerning life’s origins. Here, we report that amyloids composed of short peptides can direct the sequence-selective, regioselective and stereoselective condensation of amino acids. The addition of activated DL-arginine and DL-phenylalanine to the peptide RFRFR-NH2 in the presence of the complementary template peptide Ac-FEFEFEFE-NH2 yields the isotactic product FRFRFRFR-NH2, 1 of 64 possible triple addition products, under conditions in which the absence of template yields only single and double additions of mixed stereochemistry. The templating mechanism appears to be general in that a different amyloid formed by (Orn)V(Orn)V(Orn)V(Orn)V-NH2 and Ac-VDVDVDVDV-NH2 is regioselective and stereoselective for N-terminal, L-amino-acid addition while the ornithine-valine peptide alone yields predominantly sidechain condensation products with little stereoselectivity. Furthermore, the templating reaction is stable over a wide range of pH (5.6–8.6), salt concentration (0–4 M NaCl), and temperature (25–90 °C), making the amyloid an attractive model for a prebiotic peptide replicating system.

The building of complex systems from basic logic gates is one of the hallmarks of circuit design in electrical engineering. The question arises whether a similar strategy can be adopted for the design of artificial biological systems. In this paper, we present the design of two logic gates, a biological AND and a biological XOR. They can be combined to produce a half-adder, one of the fundamental elements of complex systems engineering, and represent a promising basis for the design of more complex genetic circuits. Design space exploration allowed us to screen gate variants, while sensitivity analysis of refined models contributed to the specific implementation of the gates at the DNA level. The XOR gate is based on two specific proteases, which reciprocally inactivate co-synthesised transcription factors. The AND gate is designed such that, in the presence of two signals, a tRNA suppresses the premature termination of T7 RNA polymerase translation. Computer models confirmed that both designs allow gate behaviour that is reasonably close to idealised gates.

Current theories on the origin of life reveal significant gaps in our understanding of the mechanisms that allowed simple chemical precursors to coalesce into the complex polymers that are needed to sustain life.The volcanic gas carbonyl sulfide (COS) is knownt oc atalyze the condensation of amino acids under aqueous conditions,b ut the reported di-, tri-, and tetra-peptides are too short to support ar egular tertiary structure.H ere,w ed emonstrate that alanine and valine,t wo of the proteinogenic amino acids believed to have been among the most abundant on aprebiotic earth, can polymerize into peptides and subsequently assemble into ordered amyloid fibers comprising ac ross-b-sheet quaternary structure following COS-activated continuous polymerization of as little as 1mm amino acid. Furthermore,this spontaneous assembly is not limited to pure amino acids,s ince mixtures of glycine,a lanine,a spartate,a nd valine yield similar structures.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: http://dx.