Nature of bone morphogenetic protein (BMP) from decalcified rabbit bone matrix

Rabbit bone morphogenetic protein (BMP) from demineralized and defatted rabbit bone matrix was partially purified. BMP activity was examined by the implantation of fractionated materials into the thigh muscle pouch of the mouse. Rabbit BMP was solubilized by both 4M guanidine hydrochloride (GuHCl) and 6M urea solutions. Crude BMP had isoelectric point precipitation at pH 3 in 6M urea and showed bone morphogenesis. Fractions eluted with 0 and 0.2 N NaCl in DEAE CL-6B ion exchange chromatography showed bone morphogenesis in each individual pH of pH 4 to pH 7 but the fraction eluted with 1.0 N NaCl did not show any activity. Sephadex G-75 filtration separated the crude material into three peaks and the peak of about 23,000 showed bone morphogenesis. In sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and isoelectric focusing, rabbit BMP was thought to be an acidic protein having a molecular weight of 24,000 with an isoelectric point around 4.85.