Unchanged antigenic properties of a nuclear non-histone protein during phylogenesis

The phyletic distribution of Sm antigen in eukaryotes has been investigated by means of immuno-chemical techniques. This nuclear antigen, which is an acidic glycoprotein of about 7S with DNA binding ability, is present in all organisms examined. Such evidence suggests a very slow evolutionary rate for at least the antigenic determinant(s) of the Sm antigen.