JBC, Vol. 251, Issue 5, 1270-1276, Mar, 1976
Activation of C55-isoprenoid alcohol phosphokinase from Staphylococcus aureus. II. Biophysical studies
R. B. Gennis, M. Sinensky and J. L. Strominger
Physicochemical techniques were used to investigate the activation of
C55-isoprenoid alcohol phosphokinase by synthetic lecithins. Complexes of
the enzyme with phospholipids were prepared using a method employing sodium
dodecyl sulfate as a protein-solubilizing agent. Circular dichorism and the
intrinsic fluorescence of the kinase were used as optical probes of protein
conformation with these complexes. No evidence for a major lipid-dependent
conformational change in the protein was observed when these complexes were
studied under conditions where the lipid mesomorphic transitions occurred.
EPR studies of mixtures of synthetic lecithins and the C55-isoprenoid
alcohol indicated a correlation between kinase activity and the rotational
diffusion rate within the hydrophobic phase. It is concluded that the lipid
physical state probably does not affect the enzyme activity by altering the
protein conformation but more likely does so by affecting the motion of the
molecular participants in the reaction.
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