Title:
Bottom-up construction of a minimal cell for the study of the emergence of life
Abstract :
Terrestrial life is thought to have emerged in the Hadean era, ~4.0-4.1 Gy ago. Before the emergence of life, chemical evolution generated a variety of molecules in the Early earth environment, some of which were employed to form the first cell-like structure: The protocell. The protocell is a hypothetical cell-form which is composed of RNA and a fatty acid membrane vesicle, where the RNA self-reproduces inside. On the other hand, all the modern cells are thought to have evolved from a hypothetical common ancestor, LUCA, which is located at the root of phylogenetic tree. Although these have been long standing as representative models of primitive cells, how the protocell developed into LUCA is still unclear. For this question, I have investigated possible cell-forms possessing fundamental properties of life through the reconstruction of core functions of the modern cell1-4. In this talk, I will present my recent work at ELSI; the reconstruction of a self-growing and -dividing artificial cell as well as an energy-independent autotrophic artificial cell. We have reconstructed a metabolic pathway for fatty acid synthesis and encapsulated it inside a cell-size membrane vesicle. We also constructed an artificial cell that can produce ATP from light energy to be used for the synthesis of proteins inside the vesicle. Through these constructive approaches, I develop a model that the membrane of the protocell shifted from fatty acids to phospholipids, which allows the emergence of functional catalysts which work in a recursive cycle to produce their own components, including phospholipids and ATP. I also present some future projects that I am planning to perform with other ELSI researchers, for example an exploring of functional peptide from random amino acids sequences, molecular condensation caused by polymer self-assembly, and so on.

1. Rampioni, G. et al. 2018. Synthetic cells produce a quorum sensing chemical signal perceived by Pseudomonas aeruginosa. Chem Commun. 54:2090-2093.
2. Furusato, T. et al. 2018. De novo synthesis of basal bacterial cell division proteins FtsZ, FtsA, and ZipA inside giant vesicles, ACS Synthetic Biology. 7:953-961.
3. Kuruma, Y. et al. 2015. The PURE system for the cell-free synthesis of membrane proteins. Nature Protocols. 10:1328-1344.
4. Matsubayashi, H. & Kuruma, Y. et al. 2014. In vitro synthesis of the E. coli Sec Translocon from DNA. Angew. Chem. Int. Ed. Engl. 53:7535-7538.