Human Bone Morphogenetic Protein-3 Mature Ligand Is Larger Than Recorded Indicating Earlier Publications Are Flawed

Bone morphogenetic protein (BMP)-3 (osteogenin) is an important regulatory cytokine during development and acts as a tumor suppressor in several cancers. BMPs are synthesized as proproteins that are cleaved by proprotein convertases to release biologically active ligands. The BMP-3 mature ligand is recorded as 16 kDa consisting of carboxy-terminal Q363-R472 (110 amino acids). The BMP-3 ligand sequence was determined based on the expectation that BMP ligands are similar in size and has not been experimentally verified. Here we show the BMP-3 ligand is S290-R472 (183 amino acids) consistent with the approximately 25 kDa BMP-3 ligand secreted from human fibroblasts. This larger ligand size is consistent with proprotein convertase cleavage site prediction and supported by analyses using liquid chromatography tandem mass spectrometry. Data are available via ProteomeXchange with identifier PXD072827. These data indicate that the human BMP-3 mature ligand is S290-R472 and that earlier studies using recombinant human BMP-3 ligand Q363-R472 are flawed.