Purification of a growth factor from pigeon milk

Aqueous extracts of pigeon milk (PM) stimulated the in vitro growth of quiescent CHO cells maintained in culture and caused precocial incisor eruption and eyelid opening in newborn mice. CM-cellulose chromatography of the growth factor of PM enhanced its biologic activity. Rechromatography of CM-active fractions in DEAE-cellulose columns yielded a single peak that was mitogenic both in vivo and in vitro. SDS-PAGE of DEAE-active fractions gave rise to a single band of molecular weight about 6000. This protein, termed as pigeon milk-derived growth factor (PMGF), yielded a single peak on gel filtration in Sephadex G-100 columns. Elution pattern of PMGF was similar to that obtained for epidermal growth factor of mouse submaxillary gland (mEGF). The chromatographic plus electrophoretic pattern, and biologic action of PMGF suggest it to be a EGF-like protein.