The C1 domain of protein kinase C as a lipid bilayer surface sensing module

The activity of membrane-associated protein kinase C (PKC) is tightly contr olled by the physical properties of the membrane lipid bilayer, in particul ar, curvature stress, which is induced by bilayer-destabilizing lipid compo nents. An important example of this is the weakened lipid headgroup interac tions induced by phosphatidylethanolamine (PE) and cholesterol. In this wor k our previous observation with a mixed isoform PKC showing a biphasic depe ndence of activity as a function of membrane curvature stress [Slater et al . (1994) J. Biol. Chem. 269, 4866-4871] was here extended to individual iso forms. The Ca2+-dependent PKC alpha, PKC beta, and PKC gamma, along with Ca 2+-independent PKC delta, but not PKC epsilon or PKC zeta, displayed a biph asic activity as a function of membrane PE content. The fluorescence anisot ropy of N-(5-dimethylaminonaphthalene-1-sulfonyl)dioleoylphosphatidylserine (dansyl-PS), which probes the lipid environment of PKC, also followed a bi phasic profile as a function of PE content for full-length PKC alpha, PKC b eta II, and PKC gamma as did the isolated Cl domain of PKC alpha. In additi on, the rotational correlation time of both PKCa and PKC delta C1-domain-as sociated sapintoxin D, a fluorescent phorbol ester, was also a biphasic fun ction of membrane lipid PE content. These results indicate that the C1 doma in acts as a sensor of the bilayer surface properties and that its conforma tional response to these effects may directly underlie the resultant effect s on enzyme activity.