The amino-acid sequence of trout-testis histone H1

The complete amino-acid sequence of 194 residues of trout testis histone H1 has been elucidated by automated Edman degradation of large peptides derived from specific cleavages at infrequent amino-acid residues. Trout testis histone H1 has a molecular weight of 19314, is only slighly microheterogeneous, and possesses pentapeptide sequences related to Ala-Ala-Ala-Lys-Lys repeated six times in the complete sequence. Although the N-terminus of histone H1 is known to be blocked, some 10% of intact trout testis H1 contains a free N-terminal alanine residue. Three seryl residues in the C-terminal half (97-194) of the molecule occur in the sequence Lys-Ser-Pro-Lys known to be phosphorylated in trout testis H1. The sequence has been compared to the known partial sequence of rabbit thymus H1. The results are consistent with a role for histone H1 in the maintenance of the higher-order structure of chromatin.