Isolation of a chloroplast N,N'-dicyclohexylcarbodiimide-binding proteolipid, active in proton translocation.

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Abstract
The N,N''-dicyclohexylcarbodiimide-binding proteolipid from lettuce chloroplast membranes was purified by a novel, rapid technique involving 1-butanol extraction and ether precipitation. Reconstitution of this proteolipid into liposomes composed of chloroplast lipids and subsequent incorporation of bacteriorhodopsin [Halobacterium halobium] resulted in the formation of liposomes exhibiting a light-dependent accumulation of protons. This accumulation was significantly enhanced upon addition of N,N''-dicyclohexylcarbodiimide at concentrations similar to those that inhibit chloroplast ATPase activity. Radioactively labeled N,N''-dicyclohexylcarbodiimide was incorporated essentially into the proteolipid of the reconstituted liposomes. These results suggest that the functional unit responsible for proton channeling in the chloroplast membrane was isolated and reconstituted in the native state.