The Reactivation of C₅₅‐Isoprenoid‐Alcohol‐Phosphokinase Apoprotein by Lipids

The reactivation of C 55 ‐isoprenoid‐alcohol phosphokinase apoprotein by a variety of lipids has been investigated. A considerable lack of specificity for the chemical structure of the activating lipid is demonstrated. Reactivation appears to occur by some physical mechanism. An electrostatic interaction of protein and lipid does not appear to be important. All active lipids found are able to swell and become hydrated in aqueous buffer. Some of these lipids were active only after sonication or in the presence of detergent. The hydrated lipid phase is concluded to activate by solubilization, as a liquid‐crystalline or micellar solvent for the extremely hydrophobic enzyme apoprotein and for the non‐hydrating C 55 ‐isoprenoid alcohol.