A dual chromatin organization in the sperm of the bivalve mollusc Spisula solidissima.

Most of the DNA in the sperm of the bivalve mollusc. Spisula solidissima, is found to be associated with a specific high-molecular-mass, protamine-like component, sharing features common both to protamines and to histones. We have found that this component coexists, in the mature sperm nucleus, with a complete set of histones, including an H1-like histone.

Structural characterization of the trypsin-resistant core in the nuclear sperm-specific protein from Spisula solidissima.

Trypsin digestion of the protamine-like protein from Spisula solidissima has revealed the existence of an internal resistant core. The peptide contains 75 amino acid residues, and its primary structure shows some conserved sequences that are common to those found in the core of the somatic histone H5 from chicken erythrocytes. The secondary structure of this core exhibits 33% antiparallel beta-sheet, 18% beta-turns, 37% random coil, and only 10% alpha-helix, in contrast to histone H5.

Transition of chromatin from the "10 nm" lower order structure, to the "30 nm" higher order structure as followed by small angle X-ray scattering.

Chromatin oligomers undergo a conformational change from a "10 nm" lower order structure at low concentration of salt to a "30 nm" higher order structure, with increasing NaCl or MgCl2 concentration. We have extended our previously reported hydrodynamic and light-scattering measurements of the folding of well-defined chicken erythrocyte chromatin fractions to include a study of the low angle X-ray scattering in solution. We show that it is feasible to identify the folding process with gradual compaction of a chain of freely joined filaments or a worm-like chain, within the limits of all the experimental data obtained.

Biochemical and physiochemical characterization of chromatin fractions with different degrees of solubility isolated from chicken erythrocyte nuclei.

Chicken erythrocyte chromatin was prepared according to two different methods [Fulmer, A. W., & Bloomfield, V.

Histone hyperacetylation: its effects on nucleosome conformation and stability.

We have prepared nucleosome particles from HeLa cells that have been subjected to butyrate treatment. Fractions containing different levels of acetylation have been obtained within the range 7-17 acetyl groups per nucleosome. We have put special emphasis in the characterization of the particles with the highest level of histone acetylation.

Nucleosome core particle structure and structural changes in solution.

The radius of gyration, Rg, of chicken erythrocyte nucleosome core particles, was found to be 4.56 (+/- 0.07) nm by small-angle X-ray scattering, independent of particle concentration and of NaCl concentration between 0.

Interaction of chromatin with NaCl and MgCl2. Solubility and binding studies, transition to and characterization of the higher-order structure.

Chicken erythrocyte chromatin containing histones H1 and H5 was carefully separated into a number of well-characterized fractions. A distinction could be made between chromatin insoluble in NaCl above about 80 mM, and chromatin soluble at all NaCl concentrations. Both chromatin forms were indistinguishable electrophoretically and both underwent the transition from the low salt "10 nm" coil to the "30 nm" higher-order structure solenoid by either raising the MgCl2 concentration to about 0.

Nucleosome core particle stability and conformational change. Effect of temperature, particle and NaCl concentrations, and crosslinking of histone H3 sulfhydryl groups.

We have studied the reversible dissociation of core size DNA from chicken erythrocyte nucleosome core particles in solutions containing 0 X 1 M to 0 X 6 M-NaCl. Dissociation increases with increasing NaCl concentration, increasing temperature and decreasing particle concentration. At high particle concentrations, no free DNA is observed below 0 X 3 M-NaCl, whereas above 0 X 3 M-NaCl a lower limit of dissociation is reached.

Interaction and conformational changes of chromatin with divalent ions.

We have investigated the interaction of divalent ions with chromatin towards a closer understanding of the role of metal ions in the cell nucleus. The first row transition metal ion chlorides MnCl2, CoCl2, NiCl2 and CuCl2 lead to precipitation of chicken erythrocyte chromatin at a significantly lower concentration than the alkali earth metal chlorides MgCl2, CaCl2 and BaCl2. A similar distinction can be made for the compaction of chromatin to the "30 nm" solenoid higher order structure which occurs at lower MeCl2 concentration in the first group but at the same MeCl2 concentration within each group.

Structural heterogeneity of reconstituted complexes of DNA with typical and intermediate protamines.

The binding of the intermediate proteins phi 1 and phi 3 from the mussel Mytilus edulis to DNA was studied in comparison with the typical protamine from the squid Loligo vulgaris using precipitation curves, thermal denaturation and X-ray diffraction techniques. The properties of protein phi 1 appear to be very close to those of typical protamines while the properties of protein phi 3 are notably different. The method of reconstitution influences the structural properties of the complexes.

Conformational study and determination of the molecular weight of highly charged basic proteins by sedimentation equilibrium and gel electrophoresis.

We study several highly charged protamines and some related proteins from the sperm of molluscs. Circular dichroism and hydrodynamic parameters obtained from the sedimentation constant and intrinsic viscosity show that these proteins behave as random coils. However, it appears that a small amount of structure is present at basic pH.

A high molecular weight nuclear basic protein from the bivalve mollusc Spisula solidissima.

A basic protein has been isolated from sperm of the bivalve Spisula solidissima. Its characteristics are reminiscent of both histone H1 and of fish protamines. It is unusual in several respects: it contains similar amounts of lysine (24.