Immunodetection of Xenopus bone morphogenetic protein-1 in adult and embryonic cells

In order to analyze biochemical properties of Xenopus bone morphogenetic pr otein-1 (XBMP-1), rabbit antiserum (alpha-B1) was raised against a syntheti c peptide (P1) corresponding to a hydrophilic N-terminal region. XBMP-1B (X tld) synthesized in the reticulocyte lysate was successfully immunoprecipit ated by this antiserum. This precipitation was completely blocked when Pi w as added to the reaction, indicating that alpha-B1 recognized XBMP-1B speci fically. In Western blot analysis, two distinct sizes of protein (107 and 3 4 kD) were detected in hind limbs in metamorphosing animals. Both proteins were detected in various adult tissues such as lung, liver, kidney, heart, muscle, intestine, brain, and testis, The mixing of the liver and muscle ex tracts, and the following detection of immunoreactive proteins suggested th at the 34 kD band was a proteolytic product of the 107 kD protein. In the e mbryonic extracts from the unfertilized egg (stage 0) to swimming tadpoles (stage 40), a 63 kD protein was detected in addition to the 107 kD protein. We also showed that the 107 kD protein was much more expressed in the anim al half of the unfertilized eggs than in the vegetal half, but that it was ubiquitously expressed in the gastrula embryos. We suggest that the 63 and 107 kD proteins correspond to full-length proteins encoded by XBMP-1A and X BMP-1B genes, and these proteins are expressed in embryo and in various adu lt tissues.