Protamines. II. Circular dichroism study of the three main components of clupeine.

The three main components YI, YII, and Z of clupeine, a protamine from herring, have been purified and characterized. The conformational preferences of clupeines have been examined as a funciton of pH, temperature, added salts, and presence of structure-disrupting agents and helix-supporting solvents using circular dichroism. It was found that these small basic proteins assume predominantly an unordered conformation in aqueous solution. Addition of counter ions, in particular perchlorate, and 2-chloroethanol induces in various amounts the onset of the right-handed alpha-helical conformation. Urea favors the statistical coil state. It was also demonstrated that in the 0.1--4.0 . 10(-1) M range, in contrast to clupeines YI and Z, the circular dichroic properties of the YII component do not seem to be sensitive to the addition of mono- and diphosphate.