Sequence of human eosinophil-derived neurotoxin cDNA: identity of deduced amino acid sequence with human nonsecretory ribonucleases

Several clones of human eosinophil-derived neurotoxin (EDN) cDNA have been isolated from a λgt10 cDNA library prepared from mRNA derived from noninduced HL-60 cells. The amino acid (aa) sequence deduced from the coding sequence of the EDN cDNA is identical to the aa sequence of urinary nonsecretory RNase. Comparison of the aa and/or nucleotide (nt) sequences of EDN and other proteins possessing ribonucleolytic activity, namely bovine seminal RNase, human and rat pancreatic RNases, eosinophil cationic protein (ECP), and human angiogenin, shows extensive identity at half-cystine residues and at aa of active sites. Differences in aa sequences at the active sites are often the result of single nt changes in the codons. The data presented here support the concept of a RNase gene superfamily containing secretory and nonsecretory RNases, angiogenin, EDN and ECP.