Are there molecules of nucleoprotamine?

A short critical review of the data related to protamine and nucleoprotamin e (DNP) structure is given. A new model is proposed for DNP structure in wh ich protamine molecules are located in channels between the DNA molecules. DNA molecules are arranged hexagonally in the x-y plane, whereas their rela tive positions with respect to the z-axis are shifted by 0, 1/3, and 2/3 of the pitch of the double helix, As a result, large cavities are formed in t hree out of six channels surrounding each DNA molecule where the large groo ves are juxtaposed. Protamine molecules are also proposed to have some seco ndary/tertiary structure prior to complex formation. Inside the channels, a protamine molecule modifies its shape to fill the large grooves of all of the three surrounding DNA molecules simultaneously, and might possibly be i n touch with other protamine molecules in neighbouring positions as well. T his disposition allows the protamine molecules to be located between DNA mo lecules without a significant increase in the lattice parameters. (C) 1999 John Wiley & Sons, Inc.