Human Spleen Histone Hl. Isolation and Amino Acid Sequence of a Main Variant, Hlb

抄録

The complete amino acid sequence of a main variant, Hlb, of human spleen histone Hl was determined, following previous determinations of human spleen histones H2B, H2A, H3, and H4. High-performance liquid chromatography on C₈ silica of the H1 fraction yielded the homogeneous Hlb subfraction; this variant was estimated to account for 60% of the total of the four H1 variants. The sequence determination was performed with four main fragments, I to IV, obtained by limited chymotryptic digestion of H1b. Together with direct sequencing by automated Edman degradation of fragments II, III, and IV, fragment I, blocked at the N-terminal, and fragment IV, the C-terminal half the Hlb molecule, were sequenced after further digestion with staphylococcal protease and others. The four fragments were aligned with three overlapping peptides each derived from chymotryptic partial fragments, I-II and I-II-Tll, and intact H1b. Carboxypeptidase digestion of intact Hlb confirmed the C-terminal sequence of the molecule. Thus, the total sequence of Hlb was completely determined; it consists of a total of 218 amino acid residues, has a molecular weight of 21, 734 in the unmodified form, and is completely acetylated at the N-terminal serine residue and partially methylated at the lysine residue 25. This sequence is compared with two mammalian somatic HI sequences.