The structure of sea-urchin-sperm histone phi 1 (H1) in chromatin and in free solution. Trypsin digestion and spectroscopic studies.
The lysine-rich H1-type histone phi 1 from the sperm of the sea urchin Arbacia lixula has been subjected to tryptic digestion in free solution at high ionic strength. Tw trypsin-resistant peptides G phi 1 and LG phi 1 have been isolated, comprising 81 and 95 amino acids respectively, i.e. about a third of the intact histone. Circular dichroism and 270-MHz proton NMR have been used to demonstrate that the smaller peptide G phi 1 contains all the secondary and tertiary structure of intact histone phi 1. It is concluded that the resistant peptides represent a compact folded portion of the histone phi 1 chain, whilst the remaining two-thirds is disordered in free solution. Trypsin digestion of Arbacia lixula nuclei, under conditions where histone phi 1 remains tightly bound to the chromatin, leads to the same resistant peptide G phi 1. From this it is concluded that in chromatin the chain region corresponding to G phi 1 is likewise folded and inaccessible to trypsin, whilst the remaining exposed residues are located periferally and probably in an extended conformation. The rather unusual H1-type histone phi 1 from sea urchin sperm thus has a three-domain structure like calf thymus H1 and chicken erythrocyte H5. The present data emphasise the fact that this three-domain structure exists in chromatin and is not merely a free-solution artefact.
D000818:Animals; D002843:Chromatin / Q000032:analysis*; D002942:Circular Dichroism; D006657:Histones; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008239:Lysine; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009994:Osmolar Concentration; D011487:Protein Conformation; D012617:Sea Urchins; D013094:Spermatozoa / Q000032:analysis*; D014357:Trypsin
D002843:Chromatin; D006657:Histones; D014357:Trypsin; D008239:Lysine