Functional reconstitution of a membrane protein in a diacetylenic polymerizable lecithin

It is shown that polymerized diacetylenic lecithins may be used for the functional reconstitution of a membrane protein. Purple membrane patches isolated from Halobacterium halobium and liposomes of the polymerizable diacetylenic lecithin 1,2-bis(10,12 tricosadiynoyl)-sn-glycero-3-phosphocholine were sonicated together to form mixed vesicles highly enriched in the polymerizable lipid. A net inward proton flow on illumination as determined by the change of pH of the external medium demonstrated the stability of the vesicular form in this mixed lipid system as well as vectorial orientation of the bacteriorhodopsin in the bilayer. When bacteriorhodopsin was incorporated in non-polymerizable lipids, irradiation with ultraviolet light resulted in complete loss of function. In the diacetylenic lipids, the loss of function was slower than the increase in polymer concentration. This demonstrates the utility of the diacetylenic lecithin system for study of interactions between membrane proteins and polymerizable lipids, as well as its potential in the development of biosensors based on membrane proteins.