CONFORMATIONAL CHARACTERISTICS OF THE DIPROTAMINE STELLINE-B AND THE PRODUCTS OF ITS CHEMICAL MODIFICATION

Circular dichroism spectroscopy was used to study the conformation of native and chemically modified stelline B, Acipenser stellatus gonadal diprotamine. Circular dichroism spectra of stelline B display feature s characteristic of fish monoprotamines and are affected by acetylatio n of the N-terminal amino group and methylation of the C-terminal carb oxy group, in a manner suggesting an increased contribution of the lef t-handed conformation. Cyclic protamine was isolated, along with dimer ic and trimeric protamine, by a combined use of water-soluble carbodii mide treatment of stelline B and high-performance liquid chromatograph y. The effective volume of hydrated stelline B molecule is 18 nm(3), a s estimated by time-resolved dielectric spectroscopy. A model of stell ine B structure based on these results assumes that the protamine mole cule is formed by left-handed helical segments, and the N- and C-termi nal amino acid residues are close to each other and probably form an i nternal salt bridge.