C 55 -isoprenoid alcohol phosphokinase: an extremely hydrophobic protein from the bacterial membrane

C(55)-isoprenoid alcohol phosphokinase, a butanol-soluble enzyme from the membrane of Staphylococcus aureus, has been purified to homogeneity by the inclusion of organic solvents in all of the techniques used. By polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, the enzyme is a single polypeptide chain of molecular weight 17,000. The amino-acid analysis reveals an unusually high content of nonpolar amino acids (58%), the largest amount so far reported in any protein. When equilibrated in butanol-water, enzyme apoprotein is found in the butanol layer. The influence of sodium chloride indicates that the lipid requirement of the enzyme is nonelectrostatic in nature.