Abstract
Lipid membranes, nucleic acids, proteins, and metabolism are essential for modern cellular life. Synthetic systems emulating the fundamental properties of living cells must therefore be built upon these functional elements. In this work, phospholipid-producing enzymes encoded in a synthetic minigenome are cell-free expressed within liposome compartments. The de novo synthesized metabolic pathway converts precursors into a variety of lipids, including the constituents of the parental liposome. Balanced production of phosphatidylethanolamine and phosphatidylglycerol is realized, owing to transcriptional regulation of the activity of specific genes combined with a metabolic feedback mechanism. Fluorescence-based methods are developed to image the synthesis and membrane incorporation of phosphatidylserine at the single liposome level. Our results provide experimental evidence for DNA-programmed membrane synthesis in a minimal cell model. Strategies are discussed to alleviate current limitations toward effective liposome growth and self-reproduction.
Highlights
Lipid membranes, nucleic acids, proteins, and metabolism are essential for modern cellular life
We aimed to reconstitute the Kennedy phospholipid synthesis pathway from E. coli starting from all seven enzyme-encoded genes (Fig. 1a)
The integral membrane protein CdsA catalyses the activation of phosphatidic acid (PA) with cytosine triphosphate (CTP) to generate diacyl-sn-glycero-3-(cytidine diphosphate)[26] which serves as a precursor for two separate branches of the Kennedy pathway
Summary
Nucleic acids, proteins, and metabolism are essential for modern cellular life. Substrates present in the external environment absorb to the membrane or diffuse across, and are transformed into molecular building blocks by metabolic processes Another aspect that is relevant when describing the inner functioning of a biological cell is the coupling between the different subsystems[7], such as genetic information, protein synthesis, and metabolic synthesis of the membrane constituents. To establish a link between the lipid compartment and its internal content, liposome growth could be made conditional to encapsulated nucleic acids[12,16] or catalysts[17] Such model systems are attractive for their molecular simplicity and may resemble primitive cells before the emergence of modern biology. We show that the synthesis of PE and PG lipids from simpler precursors can be genetically controlled inside
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