Abstract
The characterization of the function of bone morphogenetic protein-1 (BMP-1) was reported in last week9s issue of Science(19 January, p. 360). In his Perspective, A. H. Reddi explains why it was surprising (and important) that BMP-1 turned out to be identical to procollagen C-proteinase, the enzyme responsible for triggering the self-assembly of collagen.