Eosinophil cationic protein, like eosinophil-derived neurotoxin, is localized to the granule matrix of the eosinophil. Both proteins possess neurotoxic, helminthotoxic, and ribonucleolytic activities. The cDNA sequences of the genes encoding these 2 proteins and the deduced amino acid sequences indicate that the genes belong to the ribonuclease gene superfamily.

Hamann et al. (1990) demonstrated remarkable similarities of eosinophil-derived neurotoxin and eosinophil cationic protein, symbolized RNS2 and RNS3, respectively, in noncoding sequences, introns, and flanking regions, as well as the previously known coding regions. A single intron in the 5-prime untranslated region and an intronless coding region appear to be features common to many members of the RNase gene superfamily.