Modelling and Refinement of the Crystal Structure of Nucleoprotamine from Gibbuta Divaricata |
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| Authors: | L. C. Puigjaner I. Fita S. Arnott R. Chandrasekaran J. A. Subirana |
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| Affiliation: | 1. Unidad de Química Macromolecular del C.S.I.C. , Escuela Técnica Superior de Ingenieros Industriales , Diagonal, 647, 08028 , Barcelona , Spain;2. Purdue University, Department of Biological Sciences , West Lafayette , Indiana , 47907 , U.S.A.;3. Unidad de Química Macromolecular del C.S.I.C. , Escuela Técnica Superior de Ingenieros Industriales , Diagonal, 647, 08028 , Barcelona , Spain;4. Purdue University, Department of Biological Sciences , West Lafayette , Indiana , 47907 , U.S.A. |
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| Abstract: | Abstract The molecular structure of nucleoprotamine from Gibbula divaricata and its packing in oriented fibers has been modelled both to fit the X-ray diffraction pattern and to avoid steric compression. The representative model consists of 51 poly(dinucleotide) B-DNA helices with 51 poly(hexapeptide) chains associated with the major grooves. The prevailing peptide conformation is β, The four arginine residues present are hydrogen-bonded to DNA phosphates while neutral peptides protrude into the minor grooves of neighboring nucleoprotamine molecules which are packed 2.61 nm apart in a screw-disordered, quasi-hexagonal lattice. This model reconciles a number of earlier, apparently conflicting experimental results and explains the remarkable stability of nucleoprotamines. |
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