Eosinophil cationic protein cDNA. Comparison with other toxic cationic proteins and ribonucleases.

摘要: Human eosinophil granules contain several basic proteins including cationic protein (ECP), eosinophil-derived neurotoxin (EDN) and major (MBP). ECP MBP are potent helminthotoxins while EDN is less so. Both possess neurotoxic ribonuclease activities. A clone representing mRNA was isolated from an lambda ZAP cDNA library. The sequence codes for a preprotein of 160 amino acids 133 acids, the terminus which identical to known partial acid ECP. nucleotide shows similarity EDN, rat pancreatic ribonuclease, human angiogenin; all members gene superfamily. Although deduced shares active site substrate binding residues with angiogenin, activity 50 100 times than that possibly because lack positively charged residue at position 122. calculated isoelectric point (10.8), electronic charge (14.5), distribution different those but similar MBP, may account in part greater helminthotoxic when compared EDN. These data suggest derived common ancestral has evolved into helminthotoxin some respects losing much its activity.