The N-terminally acetylated form of mammalian histone H1 degrees, but not that of avian histone H5, increases with age

We report here on the HPCE separation of two chicken H5 histones, which do not show the heterogeneity (Gln/Arg) at residue 15 first found by Greenaway and Murray [Greenaway and Murray (1971) Nat. New Biol, 229, 233-238]. The two subfractions obtained were identified using reversed-phase HPLC, hydrop hilic interaction HPLC, Edman degradation, and MALDI-MS analysis. We found that the two H5 subcomponents differ only by an acetylated (designated H5a) and an unacetylated N-terminus (H5b). In contrast to the N-terminally acet ylated form of rat kidney histone H1 degrees, which increased by about 40% with aging of the animal, the corresponding form of chicken H5 did not: the ratio N-terminally acetylated: unacetylated remained constant (30:70) when histone H5 was extracted from erythrocytes of newly hatched chickens and f rom adult chickens, respectively. The HPCE technique used in this investiga tion represents a quick and convenient method for analyzing N-terminally ac etylated proteins in the presence of unacetylated forms. (C) 1999 Academic Press.