J. Biol. Chem., Vol. 256, Issue 20, 10577-10582, 10, 1981
Occurrence of H1o-like protein and protein A24 in the chromatin of bullfrog erythrocytes lacking histone 5
T Shimada, Y Okihama, C Murata and R Shukuya
Electrophoretic analysis of acid-soluble chromosomal protein isolated from
the erythrocytes of the bullfrog Rana catesbeiana reveals that the
nucleated erythrocytes contain five major histones (H1A, H2A, H2B, H3, and
H4) and three minor histone-like proteins (H1B, R1, and R2). Histone 5,
found as an additional major histone of avian erythrocytes, is not detected
in the frog erythrocytes. Three minor components of the bullfrog
erythrocytes, which are not present in the avian erythrocytes, have been
purified to electrophoretic homogeneity and characterized by amino acid
analysis, NH2-terminal analysis, tryptic peptide mapping, and immunological
techniques. H1B extracted with 5% HClO4 along with H1A has a very similar
amino acid composition and tryptic peptide map to H1o, a subfraction of
lysine-rich histones found in nondividing mammalian cells. Microcomplement
fixation also shows that H1B and bovine liver H1o share some common
antigenic determinants. R1, a basic protein having a ratio of basic/acidic
amino acids of 2.0 and 20 mol % lysine, is distinguished from any
chromosomal proteins characterized so far on the basis of electrophoretic
mobility and amino acid composition. On the other hand, R2 is identified as
protein A24 on the basis of its electrophoretic mobility, amino acid
composition, and tryptic peptide map. Since H1o and protein A24 are
considered to be involved in the inhibition of DNA replication and RNA
synthesis, respectively, H1o-like protein and protein A24 in the frog
erythrocyte lacking H5 may have central roles in genetic inactivation
during erythrocyte maturation.