Possible Molecular Evolution of Biomembranes: from Single-Chain to Double-Chain Lipids

• Published in: Chemistry & biodiversity Vol. 4; no. 5; pp. 837 - 848
• Main Authors: Gotoh, Mari, Sugawara, Ayae, Akiyoshi, Kazunari, Matsumoto, Isamu, Ourisson, Guy, Nakatani, Yoichi
• Format: Journal Article
• Language: English
• Published: Zürich WILEY-VCH Verlag 01.05.2007; WILEY‐VCH Verlag
• Subjects: Animals; Biomembranes; Cell Membrane - chemistry; Evolution, Molecular; Fluorescence microscopy; Hydrophobic and Hydrophilic Interactions; Lectin; Lectins - chemistry; Lipids; Lipids - chemistry; Molecular evolution; Polysaccharides; Polysaccharides - chemistry
• ISSN: 1612-1872; 1612-1880
• DOI: 10.1002/cbdv.200790071

We have studied a possible evolution process permitting a ‘primitive’ membrane to evolve towards a membrane structure with an outer wall, similar to that of bacteria. We have investigated whether a polysaccharide bearing hydrophobic phytyl or cholesteryl chains coats giant vesicles made of single‐ or double‐chain lipids. Phytyl‐pullulan 5b was found to bind to the surface of vesicles made of either single‐ or double‐chain lipids. In contrast, cholesteryl‐pullulan 5a only coated the surface of vesicles made of double‐chain lipids. These results indicate that there must be a close match between the size and shape of membrane constituents and the hydrophobic molecules to be inserted. This process could, thus, provide a selection mechanism of lipid‐membrane constituents during the course of biomembrane evolution. The presence of the above ‘hydrophobized’ polysaccharides on the surface of different giant vesicles was identified by lectin binding. Both concanavalin A and annexin V were shown by fluorescence microscopy to bind spontaneously to vesicles made of double‐chain lipids. Our experiments exemplify that self‐organization of amphiphiles into closed vesicles in aqueous solution automatically leads to the coating of vesicles by ‘hydrophobized’ polysaccharides, which then permit lectin binding. This is a possible mechanism for the evolution of primitive membranes towards ‘proto‐cells’.