Cross-complexing pattern of plant histones

Abstract

Pea histones H2a, H2b, H3, and H4 were isolated and their interactions studied by fluorescence anisotropy, light scatter and circular dichroism. Histones H3 and H4 are almost identical in plants and animals, but plant histones H2a and H2b differ markedly from their mammalian counterparts. Pea H2b has a MW approximately 20% greater than that of calf thymus H2b; the amino acid compositions of the 2 proteins are different. Calf thymus H2a exists as a single molecular weight species, while pea H2a exists as 2 species which differ by about 1500 daltons. The larger plant H2a is about 19% greater in MW than calf thymus H2a. The smaller is about 8% greater. Despite these differences between calf and pea histones, the strong interactions between histone pairs H3 and H4, H2b and H4, and H2a and H2b, previously demonstrated for calf histones, also exist for pea histones. There are weak interactions between pea H2a and H4 and between pea H2b and H3, and an interaction of intermediate strength between H2a and H3. The cross-complexing pattern of the plant histones is therefore the same as that reported for calf thymus histones despite the dissimilarities of H2a and H2b.