Possible molecular evolution of biomembranes: from single-chain to double-chain lipids.
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'.
Gotoh
Mari
M
Centre de Neurochimie, 5 rue Blaise Pascal, 67084 Strasbourg, France.
Sugawara
Ayae
A
Akiyoshi
Kazunari
K
Matsumoto
Isamu
I
Ourisson
Guy
G
Nakatani
Yoichi
Y
D000818:Animals; D002462:Cell Membrane / Q000737:chemistry*; D019143:Evolution, Molecular; D057927:Hydrophobic and Hydrophilic Interactions; D037102:Lectins / Q000737:chemistry; D008055:Lipids / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry
D037102:Lectins; D008055:Lipids; D011134:Polysaccharides