Very Lysine Rich Histone of Echinoderms and Molluscs

Abstract

THE similarity of the histone component F2a1 from calf and pea¹ casts doubt on the hypothesis that it acts as a selective repressor of gene activity. Such a function may, however, be fulfilled by the very lysine-rich fractions F1 because they are significantly heterogeneous in vertebrate species^2,3. Alternatively, the heterogeneity might be explained in terms of gene multiplicity and/or a modification of some amino-acid residues⁴ and may have no implication in gene regulation. It would then have an evolutionary significance, similar to that of the heterogeneity in proteins such as haemoglobin and cytochrome. We thought that it would be of interest, therefore, to study the very lysine-rich component in different species, particularly those far apart on the evolutionary scale. We chose a mollusc and an echinoderm and found that their F1 histones differed from each other in a limited but significant way and that they also differed from the equivalent F1 fraction from calf thymus.