Conformation and properties of DNA–(Lys33, Leu67)100–(Orn)20 complex: A nucleohistone model
✍ Scribed by P. Costantino; S. Verdini; P. De Santis; R. Rizzo; M. Savino
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1979
- Tongue
- English
- Weight
- 842 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
The synthesis and characterization of the block copolypeptide (Led7, LYS:'~) looOrn20, a synthetic model of histone, are reported. In neutral aqueous solutions, 80% of the etheropolypeptide block assumes an a-helical conformation, whereas the polyornithine block is in a random-coil conformation. In the association complexes with DNA, melting and titration experiments, as well as CD results, indicate that the polyornithine block interacts with DNA, whereas at least 2/3 of the lysine residues of the (Leu, Lys) moiety are excluded from the direct binding with DNA. CD spectra of the association complexes reveal significant differences from those obtained with DNA-polyornithine and DNA-polylysine complexes but substantial similarities with CD spectra of native and reconstituted nucleohistones. In contrast to DNA-polyornithine complexes, the CD spectra of the ternary complexes, copolypeptide-DNA-ethidium bromide, indicate a strong reduction of the dye intercalation. The low-angle x-ray diffraction pattern, reminiscent of that of chromatin, reveals the presence of a superstructure in these complexes. The results obtained are discussed in connection with the expected structural features of the model.