Substrate and sequential site specificity of cytoplasmic histone acetyltransferases of maize and rat liver

The cytoplasmic B-type histone acetyltransferase was purified to apparent homogeneity from maize embryos, We established a novel protocol for easy large-scale preparation of acetylated core histone species, using preparative acetic acid-urea-Triton PAGE, The pure maize histone acetyltransferase B was highly specific for histone H4 under various assay conditions, modifying H4 up to the di-acetylated isoform, Only non-acetylated H4 isoform was accepted as substrate, whereas mono-acetylated H4 could not be further acetylated. The enzyme selectively acetylated lysines 12 and 5 in a sequential manner, The same results were obtained with a partially purified cytoplasmic histone acetyltransferase of rat liver. Protein sequencing results were supported by immunological characterization of acetylated H4 subspecies with site-specific H4-acetyllysine antibodies. (C) 1998 Federation of European Biochemical Societies.