Sciatin Is a Transferrin‐Like Polypeptide

Abstract

Sciatin, an acidic glycoprotein from chicken sciatic nerve, has myotrophic effects on avian skeletal muscle cells in culture. As sciatin had certain structural similarities to transferrin, the physicochemical characteristics of sciatin were further investigated in order to determine the relationship between these 2 proteins. Sciatin was strikingly similar to ovotransferrin in amino acid composition. Amino acid sequence analysis revealed that sciatin and ovotransferrin had identical amino-terminal sequences for at least the first 20 amino acid residues. Chicken ovotransferrin, but not human seurm transferrin, cross-reacted with rabbit antisciatin antibodies upon rocket immunoelectrophoresis and double immunodiffusion in agar. In addition, in the presence of bicarbonate, sciatin bound .apprx. 2 mol Fe2+/mol protein. By use of the purification procedure developed for sciatin, a protein from chicken serum that cross-reacted with antisciatin serum was purified, migrated at a position identical to that of sciatin or ovotransferrin on 2-dimensional gel electrophoresis, had an amino composition very similar to ovotransferrin and sciatin, and had myotrophic effects on cultured musdcle cells. Sciatin is a growth-promoting polypeptide closely related in structure to transferrin.