[Conformational features of linker proteins of supercompact chromatin from marine invertebrate sperm]

A comparison of conformational potencies of linker histones of the H1 family has been performed by the curcular dichroism (CD) method. The histones were isolated from sera urchin (Strongylocentrotus intermedius), starfish (Aphelasterias japonica) and mollusc (Chlamis islandicus) sperm and rat thymus. The presence of an additional alpha-helical segment in the C-terminal part of the H1 histone from sea urchin sperm has been found to be a characteristic peculiarity of echinoderm sperm linker histones H1. The conformational properties of the H1 from starfish and sea urchin sperm are similar. The terminal domain of the mollusc sperm H1 has a more stable conformation of the left-handed helix in comparison with histones H1 of a different origin. It has been shown that the terminal fragments of the tested histones play an essential role in thermal stabilization of the secondary and ternary structures of the globular domains in these histones. The results obtained point to the difference in the mechanisms of supercondensed organization of sperm chromatin. The role of H1 histones in this process is discussed.