Spontaneous Crowding of Ribosomes and Proteins inside Vesicles: A Possible Mechanism for the Origin of Cell Metabolism

• Published in: Chembiochem : a European journal of chemical biology 2011-10, Vol.12 (15), p.2325-2330
• Main Authors: Pereira de Souza, Tereza, Steiniger, Frank, Stano, Pasquale, Fahr, Alfred, Luisi, Pier Luigi
• Format: Article
• Language: English
• Subjects: entrapment/encapsulation; Escherichia coli - genetics; Escherichia coli - metabolism; liposomes; Liposomes - metabolism; Liposomes - ultrastructure; Origin of Life; Protein Biosynthesis; Proteins - genetics; Proteins - metabolism; ribosomes; Ribosomes - genetics; Ribosomes - metabolism; Ribosomes - ultrastructure; self-assembly; Transcription, Genetic
• ISSN: 1439-4227; 1439-7633
• DOI: 10.1002/cbic.201100306

One of the open questions in the origin of life is the spontaneous formation of primitive cell‐like compartments from free molecules in solution and membranes. “Metabolism‐first” and “replicator‐first” theories claim that early catalytic cycles first evolved in solution, and became encapsulated inside lipid vesicles later on. “Compartment‐first” theories suggest that metabolism progressively occurred inside compartments. Both views have some weaknesses: the low probability of co‐entrapment of several compounds inside the same compartment, and the need to control nutrient uptake and waste release, respectively. By using lipid vesicles as early‐cell models, we show that ribosomes, proteins and lipids spontaneously self‐organise into cell‐like compartments to achieve high internal concentrations, even when starting from dilute solutions. These findings suggest that the assembly of cell‐like compartments, despite its low probability of occurrence, is indeed a physically realistic process. The spontaneous achievement of high local concentration might provide a rational account for the origin of primitive cellular metabolism. All together now: Insights into the physical mechanisms of solute entrapment in lipid vesicles were obtained by cryo‐TEM imaging. The spontaneous encapsulation of ribosomes and of the transcription/translation machinery inside a few “super‐filled” vesicles was unexpected on the basis of Poisson distribution, and might help to explain the origin of primitive cells.