Solubilized and insolubilized bone morphogenetic protein

A bone morphogenetic protein (BMP) obtained in solution by digestion of demineralized rabbit cortical bone matrix with bacterial collagenase retains its biologically active conformation in a neutral salt/ethylene glycol mixture. BMP may be insolubilized by coprecipitation with calcium phosphate and resolubilized by chemical extraction with a neutral salt in the same solvent mixture. Upon concanavalin A-Sepharose chromatography, BMP is bound by hydrophobic interaction and carbohydrate recognition and is recovered by elution with either alpha-methyl mannoside or ethylene glycol solvent mixture. Implants of both eluates and the extracts of the coprecipitate in double-walled diffusion chambers induce transmembrane bone morphogenesis. BMP is not species specific; rabbit BMP induces new bone formation in the rat. The present observations indicate that BMP is a glycoprotein.