PURIFICATION, CHARACTERIZATION, AND CDNA CLONING OF A NOVEL GROWTH-FACTOR FROM THE CONDITIONED MEDIUM OF NIH-SAPE-4, AN EMBRYONIC-CELL LINEOF SARCOPHAGA-PEREGRINA (FLESH FLY)

A growth factor from the conditioned medium of NIH-Sape-4, an embryoni c cell line of the flesh fly, was purified to homogeneity. This growth factor, termed IDGF, stimulated the proliferation of NIH-Sape-4 cells in an autocrine manner; it was a homodimer of a protein with a molecu lar mass of 52 kDa, and its specific activity was comparable with thos e of mammalian growth factors, Immunoblotting experiments revealed tha t unfertilized mature eggs of the flesh fly contained this growth fact or, a certain level of which was maintained throughout embryonic devel opment, Analysis of cDNA for this growth factor showed that this facto r is a novel protein consisting of 553 amino acid residues, No signifi cant sequence similarity was found between this factor and other prote ins except atrial gland granule-specific antigen of Aplysia californic a.