CONFORMATION OF THE ABORTIFACIENT PROTEIN PINELLIN - A CIRCULAR DICHROIC STUDY

The conformation of pinellin was studied by circular dichroism, which showed a minimum at 223 nm and a double maximum at 198-200 nm. The protein was rich in beta-sheet (about 40%) with little alpha-helix, based on current CD analyses. It was stable between pH 4 and 10 beyond which it unfolded reversibly, but in alkaline solution, prolongly stored at, say, pH 12, it became irreversibly denatured. Thermal denaturation indicated a transition between 55-degrees and 68-degrees-C; the solution at 80-degrees-C was partially renatured upon air-cooling back to room temperature. Addition of sodium dodecyl sulfate caused a sharp increase in alpha-helix, which leveled off at 0.25 mM surfactant.